Zoom optical system, imaging device and method for manufacturing the zoom optical system

ABSTRACT

A zoom optical system includes, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. At least a part of the third lens group is arranged to be movable along an optical axis as a focusing lens group, and the focusing lens group is moved toward an image when a focusing state on a long-distance object is changed to a focusing state on a short-distance object. The following conditional expression is satisfied: 0.90&lt;f3/fw&lt;1.50, where f3 denotes a focal length of the third lens group and fw denotes a focal length of the zoom optical system in a wide-angle end state.

TECHNICAL FIELD

The present invention relates to a zoom optical system, an imaging device, and a method for manufacturing the zoom optical system.

TECHNICAL BACKGROUND

Proposals have so far been made on zoom optical systems suitable for photographic cameras, electronic still cameras, video cameras, and the like (for example, see Patent Documents 1 and 2).

PRIOR ARTS LIST Patent Document

Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-42557(A)

Patent Document 2: Japanese Laid-Open Patent Publication No. S63-298210(A)

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, a conventional zoom optical system has faced a problem of large variations in aberration upon zooming. Moreover, in order to achieve higher image quality, the system is desired to have an image blur correction mechanism for correcting an image blur caused by camera shake, or the like.

Moreover, the conventional zoom optical system has faced problems of large variations in aberration upon zooming and large variations in aberration upon focusing on a short distance object.

Moreover, a zoom optical system having further successful optical performance has been recently required.

Means to Solve the Problems

A zoom optical system according to a first aspect of the invention is formed of, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which at least a part of the second lens group or at least a part of the third lens group is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis, and the following conditional expression is satisfied: 4.40<f1/(−f2)<8.00

where f1 denotes a focal length of the first lens group, and

f2 denotes a focal length of the second lens group.

An imaging device according to a first aspect of the invention is provided with the zooming optical system according to the first aspect of the invention.

A zoom optical system according to a second aspect of the invention has, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which at least a part of the second lens group or at least a part of the third lens group is configured to be moveable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis, and the following conditional expression is satisfied: 3.60<f1/f3<8.00

where f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

An imaging device according to a second aspect of the invention is provided with the zooming optical system according to the second aspect of the invention.

A zoom optical system according to a third aspect of the invention is formed of, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which, upon zooming from a wide-angle end state to a telephoto end state, focusing is made by moving the first lens group to a direction of the object along an optical axis direction and moving at least a part of the third lens group along the optical axis direction, and the following conditional expression is satisfied: 0.73<(−f2)/f3<2.00

where f2 denotes a focal length of the second lens group, and

f3 denotes a focal length of the third lens group.

An imaging device according to a third aspect of the invention is provided with the zooming optical system according to the third aspect of the invention.

A zoom optical system according to a fourth aspect of the invention has, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which, upon zooming from a wide-angle end state to a telephoto end state, the first lens group is moved to a direction of the object along an optical axis direction, and the following conditional expressions are satisfied: 0.14<fw/f1<0.26 0.77<fw/f3<1.05

where fw denotes a focal length of the zoom optical system in the wide-angle end state,

f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

An imaging device according to a fourth aspect of the invention is provided with the zooming optical system according to the fourth aspect of the invention.

A zoom optical system according to a fifth aspect of the invention has, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which focusing is made by moving at least a part of the third lens group along an optical axis direction, and the following conditional expression is satisfied: 0.90<f3/fw<1.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

An imaging device according to a fifth aspect of the invention is provided with the zooming optical system according to the fifth aspect of the invention.

A zoom optical system according to a sixth aspect of the invention has, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which at least a part of the third lens group is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis, and the following conditional expression is satisfied: 0.60<f3/fw<3.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

An imaging device according to a sixth aspect of the invention is provided with the zooming optical system according to the sixth aspect of the invention.

A method for manufacturing a zoom optical system according to a first aspect of the invention refers to the method including, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which each lens is arranged within a lens barrel in such a manner that at least a part of the second lens group or at least a part of the third lens group is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis, and the following expression is satisfied: 4.40<f1/(−f2)<8.00

where f1 denotes a focal length of the first lens group, and

f2 denotes a focal length of the second lens group.

A method for manufacturing a zoom optical system according to a second aspect of the invention refers to the method including, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which each lens is arranged within a lens barrel in such a manner that at least a part of the second lens group or at least a part of the third lens group is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis, and the following expression is satisfied: 3.60<f1/f3<8.00

where f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

A method for producing a zoom optical system according to a third aspect of the invention refers to the method including, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having negative refractive power, in which each lens is arranged within a lens barrel in such a manner that, upon zooming from a wide-angle end state to a telephoto end state, focusing is made by moving the first lens group to a direction of the object along an optical axis direction, and moving at least apart of the lens group along the optical axis direction, and the following expression is satisfied: 0.73<(−f2)/f3<2.00

where f2 denotes a focal length of the second lens group, and

f3 denotes a focal length of the third lens group.

A method for producing a zoom optical system according to a fourth aspect of the invention refers to the method including, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having negative refractive power, in which each lens is arranged within a lens barrel in such a manner that, upon zooming from a wide-angle end state to a telephoto end state, the first lens group is moved to a direction of the object along an optical axis direction, and the following expressions are satisfied: 0.14<fw/f1<0.26 0.77<fw/f3<1.05

where fw denotes a focal length of the zoom optical system in the wide-angle end state,

f1 denotes a focal length of the first lens group, and

f3 denotes a focal length of the third lens group.

A method for manufacturing a zoom optical system according to a fifth aspect of the invention refers to the method including, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which each lens is arranged within a lens barrel in such a manner that focusing is made by moving at least a part of the third lens group along an optical axis direction, and the following expression is satisfied: 0.90<f3/fw<1.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

A method for manufacturing a zoom optical system according to a sixth aspect of the invention refers to the method having, disposed in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, in which each lens is arranged within a lens barrel in such a manner that at least a part of the third lens group is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis, and the following expression is satisfied: 0.60<f3/fw<3.50

where f3 denotes a focal length of the third lens group, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a lens configuration of a zoom optical system according to Example 1.

FIGS. 2A, 2B and 2C are graphs showing aberrations of the zoom optical system (according to Example 1) in a wide-angle end state (f=18.500), in which FIG. 2A is graphs showing various aberrations upon focusing on infinity, FIG. 2B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0196), and FIG. 2C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 3A, 3B and 3C are graphs showing aberrations of the zoom optical system (according to Example 1) in an intermediate focal length state (f=35.000), in which FIG. 3A is graphs showing various aberrations upon focusing on infinity, FIG. 3B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0365), and FIG. 3C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 4A, 4B and 4C are graphs showing aberrations of the zoom optical system (according to Example 1) in a telephoto end state (f=53.500), in which FIG. 4A is graphs showing various aberrations upon focusing on infinity, FIG. 4B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0554), and FIG. 4C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIG. 5 is a cross-sectional view showing a lens configuration of a zoom optical system according to Example 2.

FIGS. 6A, 6B and 6C are graphs showing aberrations of the zoom optical system (according to Example 2) in a wide-angle end state (f=18.500), in which FIG. 6A is graphs showing various aberrations upon focusing on infinity, FIG. 6B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0196), and FIG. 6C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 7A, 7B and 7C are graphs showing aberrations of the zoom optical system (according to Example 2) in an intermediate focal length state (f=34.176), in which FIG. 7A is graphs showing various aberrations upon focusing on infinity, FIG. 7B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0358), and FIG. 7C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 8A, 8B and 8C are graphs showing aberrations of the zoom optical system (according to Example 2) in a telephoto end state (f=53.500), in which FIG. 8A is graphs showing various aberrations upon focusing on infinity, FIG. 8B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0556), and FIG. 8C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIG. 9 is a cross-sectional view showing a lens configuration of a zoom optical system according to Example 3.

FIGS. 10A, 10B and 10C are graphs showing aberrations of the zoom optical system (according to Example 3) in a wide-angle end state (f=18.477), in which FIG. 10A is graphs showing various aberrations upon focusing on infinity, FIG. 10B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0194), and FIG. 10C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 11A, 11B and 11C are graphs showing aberrations of the zoom optical system (according to Example 3) in an intermediate focal length state (f=34.000), in which FIG. 11A is graphs showing various aberrations upon focusing on infinity, FIG. 11B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0355), and FIG. 11C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 12A, 12B and 12C are graphs showing aberrations of the zoom optical system (according to Example 3) in a telephoto end state (f=53.500), in which FIG. 12A is graphs showing various aberrations upon focusing on infinity, FIG. 12B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0552), and FIG. 12C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIG. 13 is a cross-sectional view showing a lens configuration of a zoom optical system according to Example 4.

FIGS. 14A, 14B and 14C are graphs showing aberrations of the zoom optical system (according to Example 4) in a wide-angle end state (f=18.500), in which FIG. 14A is graphs showing various aberrations upon focusing on infinity, FIG. 14B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0194), and FIG. 14C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 15A, 15B and 15C are graphs showing aberrations of the zoom optical system (according to Example 4) in an intermediate focal length state (f=34.061), in which FIG. 15A is graphs showing various aberrations upon focusing on infinity, FIG. 15B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0355), and FIG. 15C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIGS. 16A, 16B and 16C are graphs showing aberrations of the zoom optical system (according to Example 4) in a telephoto end state (f=53.500), in which FIG. 16A is graphs showing various aberrations upon focusing on infinity, FIG. 16B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0556), and FIG. 16C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity.

FIG. 17 is a substantial cross-sectional view showing a configuration of a camera according to each of first to fourth embodiments.

FIG. 18 is a flowchart for describing a method for manufacturing the zoom optical system according to the first embodiment.

FIG. 19 is a flowchart for describing a method for manufacturing the zoom optical system according to the second embodiment.

FIG. 20 is a flowchart for describing a method for manufacturing the zoom optical system according to the third embodiment.

FIG. 21 is a flowchart for describing a method for manufacturing the zoom optical system according to the fourth embodiment.

FIG. 22 is a cross-sectional view showing a lens configuration of a zoom optical system according to Example 5.

FIGS. 23A, 23B and 23C are graphs showing aberrations of the zoom optical system (according to Example 5) in a wide-angle end state (f=18.50), in which FIG. 23A is graphs showing various aberrations upon focusing on infinity, FIG. 23B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 23C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.009).

FIGS. 24A, 24B and 24C are graphs showing aberrations of the zoom optical system (according to Example 5) in an intermediate focal length state (f=34.95), in which FIG. 24A is graphs showing various aberrations upon focusing on infinity, FIG. 24B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 24C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.018).

FIGS. 25A, 25B and 25C are graphs showing aberrations of the zoom optical system (according to Example 5) in a telephoto end state (f=53.50), in which FIG. 25A is graphs showing various aberrations upon focusing on infinity, FIG. 25B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 25C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.027).

FIG. 26 is a cross-sectional view showing a lens configuration of a zoom optical system according to Example 6.

FIGS. 27A, 27B and 27C are graphs showing aberrations of the zoom optical system (according to Example 6) in a wide-angle end state (f=18.74), in which FIG. 27A is graphs showing various aberrations upon focusing on infinity, FIG. 27B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 27C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.010).

FIGS. 28A, 28B and 28C are graphs showing aberrations of the zoom optical system (according to Example 6) in an intermediate focal length state (f=34.50), in which FIG. 28A is graphs showing various aberrations upon focusing on infinity, FIG. 28B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 28C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.018).

FIGS. 29A, 29B and 29C are graphs showing aberrations of the zoom optical system (according to Example 6) in a telephoto end state (f=52.08), in which FIG. 29A is graphs showing various aberrations upon focusing on infinity, FIG. 29B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 29C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.026).

FIG. 30 is a cross-sectional view showing a lens configuration of a zoom optical system according to Example 7.

FIGS. 31A, 31B and 31C are graphs showing aberrations of the zoom optical system (according to Example 7) in a wide-angle end state (f=18.72), in which FIG. 31A is graphs showing various aberrations upon focusing on infinity, FIG. 31B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 31C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.010).

FIGS. 32A, 32B and 32C are graphs showing aberrations of the zoom optical system (according to Example 7) in an intermediate focal length state (f=35.50), in which FIG. 32A is graphs showing various aberrations upon focusing on infinity, FIG. 32B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 32C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.018).

FIGS. 33A, 33B and 33C are graphs showing aberrations of the zoom optical system (according to Example 7) in a telephoto end state (f=52.00), in which FIG. 33A is graphs showing various aberrations upon focusing on infinity, FIG. 33B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 33C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.027).

FIG. 34 is a substantial cross-sectional view showing a configuration of a camera according to each of fifth and sixth embodiments.

FIG. 35 is a flowchart for describing a method for manufacturing the zoom optical system according to the fifth embodiment.

FIG. 36 is a flowchart for describing a method for manufacturing the zoom optical system according to the sixth embodiment.

DESCRIPTION OF THE EMBODIMENTS (FIRST TO FOURTH EMBODIMENTS)

Hereinafter, a first embodiment will be described with reference to drawings. As shown in FIG. 1, a zoom optical system ZL according to the first embodiment is formed of, disposed in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

According to this configuration, size reduction of a lens barrel and securement of a sufficient zoom ratio in a wide-angle end state can be achieved.

In the zoom optical system ZL according to the first embodiment, at least a part of the second lens group G2 or at least a part of the third lens group G3 is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis.

According to this configuration, size reduction of an image blur correction mechanism including the vibration-proof lens group can be achieved.

Then, under the configuration, the following conditional expression (1) is satisfied: 4.40<f1/(−f2)<8.00  (1)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (1) specifies a proper ratio of the focal length of the first lens group G1 to the focal length of the second lens group G2. Successful optical performance and size reduction of an optical system can be achieved by satisfying the conditional expression (1).

If the ratio thereof is less than a lower limit of the conditional expression (1), refractive power of the first lens group G1 increases, and correction of coma aberration, astigmatism, and curvature of field in a telephoto end state becomes difficult, and therefore such a case is not preferable.

An effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (1) to 5.00.

If the ratio thereof is more than an upper limit of the conditional expression (1), refractive power of the second lens group G2 increases, correction of coma aberration and astigmatism in a wide-angle end state becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upper limit of the conditional expression (1) to 7.00.

In the zoom optical system ZL according to the first embodiment, zooming is preferably made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3.

According to this configuration, while variations in spherical aberration and curvature of field upon zooming are suppressed, a sufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the first embodiment, the third lens group G3 is formed of, disposed in order from an object, a 31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33, in which the 32nd lens group G32 is preferably configured to be movable, as the vibration-proof lens group, so as to have a component in a direction perpendicular to an optical axis.

According to this configuration, successful optical performance can be realized upon correcting the image blur (vibration proofing). Size reduction of the image blur correction mechanism can also be achieved.

In the zoom optical system ZL according to the first embodiment, the 32nd lens group G32 preferably has negative refractive power.

According to this configuration, successful optical performance can be realized upon correcting the image blur (vibration proofing).

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expression (2): 2.00<(−f32)/f3<6.00  (2)

where f32 denotes a focal length of the 32nd lens group G32, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (2) specifies a proper ratio of the focal length of the 32nd lens group G32 to the focal length of the third lens group G3. Successful optical performance upon correcting the image blur (vibration proofing) and size reduction of the optical system can be achieved by satisfying the conditional expression (2).

If the ratio thereof is less than a lower limit of the conditional expression (2), refractive power of the third lens group G3 is reduced, size reduction of the lens barrel becomes difficult. If the refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (2) to 2.50.

If the ratio thereof is more than an upper limit of the conditional expression (2), refractive power of the third lens group G3 increases, correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable. Refractive power of the 32nd lens group G32 also increases, and a shift amount upon correcting the image blur (vibration proofing) increases, and size reduction of the lens barrel becomes difficult.

The effect of the first embodiment can be ensured by setting the upper limit of the conditional expression (2) to 4.00.

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expression (3): 0.50<|f31|/f3<2.00  (3)

where f31 denotes a focal length of the 31st lens group G31, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (3) specifies a proper ratio of the focal length of the 31st lens group 31 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (3).

If the ratio thereof is less than a lower limit of the conditional expression (3), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (3) to 0.70.

If the ratio thereof is more than an upper limit of the conditional expression (3), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upper limit of the conditional expression (3) to 1.50.

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expression (4): 1.00<|f33|/f3  (4)

where f33 denotes a focal length of the 33rd lens group G33, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (4) specifies a proper ratio of the focal length of the 33rd lens group G33 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (4).

If the ratio thereof is less than a lower limit of the conditional expression (4), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If the refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (4) to 2.00.

In the zoom optical system ZL according to the first embodiment, the 32nd lens group G32 is preferably configured of a single lens.

According to this configuration, variations in decentering coma aberration and variations in curvature of field upon correcting the image blur can be successfully suppressed. Moreover, size reduction of the image blur correction mechanism can also be achieved.

The zoom optical system ZL according to the first embodiment has a stop S, and the stop S preferably moves along an optical axis direction integrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can be simplified and size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the first embodiment has a stop S, and the stop S is preferably arranged between the second lens group G2 and an image surface I.

According to this configuration, curvature of field and astigmatism can be successfully corrected.

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expression (5): 30.00°<ωw<80.00°  (5)

where ωw denotes a half angle of view in a wide-angle end state.

The conditional expression (5) represents a condition specifying a value of an angle of view in a wide-angle end state. While the zoom optical system ZL has a wide angle of view, coma aberration, distortion, and curvature of field can be successfully corrected by satisfying the conditional expression (5).

Further successful aberration correction can be made by setting the lower limit of the conditional expression (5) to 33.00°. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (5) to 36.00°.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (5) to 77.00°.

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expression (6): 2.00<ft/fw<15.00  (6)

where ft denotes a focal length of the zoom optical system in the telephoto end state, and

fw denotes a focal length of the zoom optical system in a wide-angle end state.

The conditional expression (6) represents a condition specifying a ratio of the focal length of the zoom optical system in the telephoto end state to the focal length of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, a high zoom ratio can be obtained, and simultaneously spherical aberration and coma aberration can also be successfully corrected by satisfying the conditional expression (6).

Further successful aberration correction can be made by setting the lower limit of the conditional expression (6) to 2.30. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (6) to 2.50. An effect of the first embodiment can be exhibited to a maximum by setting the lower limit of the conditional expression (6) to 2.70.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (6) to 10.00. Still further successful aberration correction can be made by setting the upper limit of the conditional expression (6) to 7.00.

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expression (7): 3.60<f1/f3<8.00  (7)

where f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (7) specifies a proper ratio of the focal length of the first lens group G1 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (7).

If the ratio thereof is less than a lower limit of the conditional expression (7), refractive power of the first lens group G1 increases, correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (7) to 3.80.

If the ratio thereof is more than an upper limit of the conditional expression (7), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upper limit of the conditional expression (7) to 7.00.

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expression (8): 0.73<(−f2)/f3<2.00  (8)

where f2 denotes a focal length of the second lens group G2, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (8) specifies a proper ratio of the focal length of the second lens group G2 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (8).

If the ratio thereof is less than a lower limit of the conditional expression (8), refractive power of the second lens group G2 increases, correction of coma aberration and astigmatism in a wide-angle end state becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (8) to 0.75.

If the ratio thereof is more than an upper limit of the conditional expression (8), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upper limit of the conditional expression (8) to 1.20.

The zoom optical system ZL according to the first embodiment preferably satisfies the following conditional expressions (9) and (10): 0.14<fw/f1<0.26  (9) 0.77<fw/f3<1.05  (10)

where fw denotes a focal length of the zoom optical system in a wide-angle end state,

f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (9) specifies a proper ratio of the focal length of the zoom optical system in the wide-angle end state to the focal length of the first lens group G1. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (9).

If the ratio thereof is less than a lower limit of the conditional expression (9), refractive power of the first lens group G1 is reduced, and size reduction of the lens barrel becomes difficult. If the refractive power of the second lens of the group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (9) to 0.15.

If the ratio thereof is more than an upper limit of the conditional expression (9), refractive power of the first lens group G1 increases, correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upper limit of the conditional expression (9) to 0.25.

The conditional expression (10) specifies a proper ratio of the focal length of the zoom optical system in the wide-angle end state to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (10).

If the ratio thereof is less than a lower limit of the conditional expression (10), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the lower limit of the conditional expression (10) to 0.80.

If the ratio thereof is more than an upper limit of the conditional expression (10), refractive power of the third lens group G3 increases, correction of spherical aberration, coma aberration, and astigmatism becomes difficult, and therefore such a case is not preferable.

The effect of the first embodiment can be ensured by setting the upper limit of the conditional expression (10) to 1.02.

The zoom optical system ZL according to the first embodiment preferably has, disposed in order from an object, a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4, and an air distance between the third lens group G3 and the fourth lens group G4 is preferably varied upon zooming.

According to this configuration, while variations in spherical aberration and curvature of field upon zooming are suppressed, a sufficient zoom ratio can be ensured.

According to the first embodiment as described above, while the zoom optical system ZL is provided with the image blur correction mechanism, the zoom optical system ZL having high optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoom optical system ZL will be described with reference to FIG. 17. As shown in FIG. 17, the camera 1 is an interchangeable lens camera (so-called mirrorless camera) provided with the above-mentioned zoom optical system ZL as an imaging lens 2.

In the camera 1, light from an object (subject) (not shown) is collected by the imaging lens 2 to form a subject image on an imaging surface of an imaging unit 3 through an OLPF (optical low pass filter) (not shown). The subject image is then subjected to photoelectric conversion by a photoelectric conversion element provided in the imaging unit 3 to produce an image of the subject. This image is displayed on an EVF (electronic view finder) 4 provided in the camera 1. Thus, a photographer can observe the subject through the EVF 4.

Moreover, if a release bottom (not shown) is pressed by the photographer, the image of the subject produced in the imaging unit 3 is stored in a memory (not shown). Thus, the photographer can photograph the subject by the camera 1.

As is known also from each Example described later, while the zoom optical system ZL is provided with the image blur correction mechanism, the zoom optical system ZL according to the first embodiment, mounted in the camera 1 as the imaging lens 2, has high optical performance by the characteristic lens configuration. Thus, according to the present camera 1, while the imaging device is provided with the image blur correction mechanism, the imaging device having high optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL is mounted on a single-lens reflex camera that has a quick return mirror and observes the subject by a finder optical system, an effect similar to the effect of the camera 1 can be produced. Moreover, even when the above-mentioned zoom optical system ZL is mounted on a video camera, an effect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZL having the configuration will be generally described with reference to FIG. 18. First, each lens is arranged within a lens barrel in such a manner that a zoom optical system ZL is formed of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having negative refractive power (step S110). At this time, at least a part of the second lens group G2 or at least a part of the third lens group G3 is configured to be movable, as a vibration-proof lens group for correcting the image blur caused by camera shake or the like, so as to have a component in a direction perpendicular to the optical axis (step ST120). Each lens is arranged within a lens barrel in such a manner that at least the following conditional expression (1) is satisfied among the conditional expressions (step ST130): 4.40<f1/(−f2)<8.00  (1)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

To take a lens arrangement according to the first embodiment as one example, as shown in FIG. 1, as a first lens group G1, in order from an object, a cemented lens formed by cementing a negative meniscus lens L11 and a positive meniscus lens L12 each having a convex surface facing the object is arranged. As a second lens group G2, in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, a biconvex lens L23, and a negative meniscus lens L24 having a concave surface facing the object are arranged. As a third lens group G3, in order from the object, a positive meniscus lens L31 having a concave surface facing the object, a cemented lens formed by cementing a biconvex lens L32 and a biconcave lens L33, a biconcave lens L34, a biconvex lens L35, a biconvex lens L36, and a negative meniscus lens L37 having a concave surface facing the object are arranged. Moreover, each lens is arranged in such a manner that the conditional expression (1) (a corresponding value of the conditional expression (1) is 5.33) is satisfied.

According to the method for manufacturing the zoom optical system related to the first embodiment as described above, while the zoom optical system ZL is provided with the image blur correction mechanism, the zoom optical system ZL having high optical performance can be realized.

Next, a second embodiment will be described with reference to drawings. As shown in FIG. 1, a zoom optical system ZL according to the second embodiment has, disposed in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

According to this configuration, size reduction of the lens barrel and securement of a sufficient zoom ratio in the wide-angle end state can be achieved.

In the zoom optical system ZL according to the second embodiment, at least a part of the second lens group G2 or at least a part of the third lens group G3 is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to the optical axis.

According to this configuration, size reduction of the image blur correction mechanism, including the vibration-proof lens group, can be achieved.

Then, under the configuration, the following conditional expression (11) is satisfied: 3.60<f1/f3<8.00  (11)

where f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (11) specifies a proper ratio of the focal length of the first lens group G1 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (11).

If the ratio thereof is less than a lower limit of the conditional expression (11), refractive power of the first lens group G1 increases, and correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult, and therefore such a case is not preferable.

An effect of the second embodiment can be ensured by setting the lower limit of the conditional expression (11) to 3.80.

If the ratio thereof is more than an upper limit of the conditional expression (11), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the upper limit of the conditional expression (11) to 7.00.

In the zoom optical system ZL according to the second embodiment, zooming is preferably made by varying an air distance between the first lens group G1 and the second lens group G2, an air distance between the second lens group G2 and the third lens group G3.

According to this configuration, while variations in spherical aberration and curvature of field upon zooming are suppressed, a sufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the second embodiment, the third lens group G3 is formed of, disposed in order from an object, a 31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33, and the 32nd lens group G32 is preferably configured to be movable, as a vibration-proof lens group, so as to have a component in a direction perpendicular to the optical axis.

According to this configuration, successful optical performance can be realized upon correcting the image blur (vibration proofing). Moreover, size reduction of the image blur correction mechanism can also be achieved.

In the zoom optical system ZL according to the second embodiment, the 32nd lens group G32 preferably has negative refractive power.

According to this configuration, successful optical performance can be realized upon correcting the image blur (vibration proofing).

The zoom optical system ZL according to the second embodiment preferably satisfies the following conditional expression (12): 2.00<(−f32)/f3<6.00  (12)

where f32 denotes a focal length of the 32nd lens group G32, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (12) specifies a proper ratio of the focal length of the 32nd lens group to the focal length of the third lens group G3. Successful optical performance upon correcting the image blur (vibration proofing) and size reduction of the optical system can be achieved by satisfying the conditional expression (12).

If the ratio thereof is less than a lower limit of the conditional expression (12), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the lower limit of the conditional expression (12) to 2.50.

If the ratio thereof is more than an upper limit of the conditional expression (12), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable. Moreover, refractive power of the 32nd lens group G32 is reduced and a shift amount upon correcting the image blur (vibration proofing) increases, and size reduction of the lens barrel becomes difficult, and therefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the upper limit of the conditional expression (12) to 4.00.

The zoom optical system ZL according to the second embodiment preferably satisfies the following conditional expression (13): 0.50<|f31|/f3<2.00  (13)

where f31 denotes a focal length of the 31st lens group G31, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (13) specifies a proper ratio of the focal length of the 31st lens group G31 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (13).

If the ratio thereof is less than a lower limit of the conditional expression (13), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the lower limit of the conditional expression (13) to 0.70.

If the ratio thereof is more than an upper limit of the conditional expression (13), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the upper limit of the conditional expression (13) to 1.50.

The zoom optical system ZL according to the second embodiment preferably satisfies the following conditional expression (14): 1.00<|f33|/f3  (14)

where f33 denotes a focal length of the 33rd lens group G33, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (14) specifies a proper ratio of the focal length of the 33rd lens group G33 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (14).

If the ratio thereof is less than a lower limit of the conditional expression (14), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the second embodiment can be ensured by setting the lower limit of the conditional expression (14) to 2.00.

In the zoom optical system ZL according to the second embodiment, the 32nd lens group G32 is preferably configured of a single lens.

According to this configuration, variations in decentering coma aberration and variations in curvature of field upon correcting the image blur can be successfully corrected. Moreover, size reduction of the image blur correction mechanism can also be achieved.

The zoom optical system ZL according to the second embodiment has a stop S, and the stop S preferably moves along an optical axis direction integrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can be simplified, and size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the second embodiment has a stop S, and the stop S is preferably arranged between the second lens group G2 and the image surface I.

According to this configuration, curvature of field and astigmatism can be successfully corrected.

The zoom optical system ZL according to the second embodiment preferably satisfies the following conditional expression (15): 30.00°<ωw<80.00°  (15)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (15) represents a condition specifying a value of an angle of view in the wide-angle end state. While the zoom optical system ZL has a wide angle of view, coma aberration, distortion, and curvature of field can be successfully corrected by satisfying the conditional expression (15).

Further successful aberration correction can be made by setting a lower limit of the conditional expression (15) to 33.00°. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (15) to 36.00°.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (15) to 77.00.

The zoom optical system ZL according to the second embodiment preferably satisfies the following conditional expression (16): 2.00<ft/fw<15.00  (16)

where ft denotes a focal length of the zoom optical system in the telephoto end state, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

The conditional expression (16) represents a condition specifying a ratio of the focal length of the zoom optical system in the telephoto end state to the focal length of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, a high zoom ratio can be obtained, and simultaneously spherical aberration and coma aberration can be successfully corrected by satisfying the conditional expression (16).

Further successful aberration correction can be made by setting a lower limit of the conditional expression (16) to 2.30. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (16) to 2.50. An effect of the second embodiment can be exhibited to a maximum by setting the lower limit of the conditional expression (16) to 2.70.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (16) to 10.00. Still further successful aberration correction can be made by setting the upper limit of the conditional expression (16) to 7.00.

According to the second embodiment as described above, while the zoom optical system ZL is provided with the image blur correction mechanism, the zoom optical system ZL having high optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoom optical system ZL will be described with reference to FIG. 17. The camera 1 is identical with the camera 1 in the first embodiment, and the configuration thereof has been already described, and the description herein is omitted.

As is known also from each Example described later, while the zoom optical system ZL is provided with the image blur correction mechanism, the zoom optical system ZL according to the second embodiment, mounted in the camera 1 as the imaging lens 2, has high optical performance by the characteristic lens configuration. Thus, according to the present camera 1, while the imaging device is provided with the image blur correction mechanism, the imaging device having high optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL is mounted on a single-lens reflex camera that has a quick return mirror and observes the subject by a finder optical system, an effect similar to the effect of the camera 1 can be produced. Moreover, even when the above-mentioned zoom optical system ZL is mounted on a video camera, an effect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZL having the configuration will be generally described with reference to FIG. 19. First, each lens is arranged within a lens barrel in such a manner that a zoom optical system ZL has a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power (step ST210). At this time, at least a part of the second lens group G2 or at least a part of the third lens group G3 is configured to be movable, as a vibration-proof lens group for correcting an image blur (caused by camera shake or the like), so as to have a component in a direction perpendicular to an optical axis (step ST220). Each lens is arranged within the lens barrel in such a manner that at least the following conditional expression (11) among the conditional expressions (step ST230): 3.60<f1/f3<8.00  (11)

where f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

To take a lens arrangement according to the second embodiment as one example, as shown in FIG. 1, as the first lens group G1, in order from an object, a cemented lens formed by cementing a negative meniscus lens L11 and a positive meniscus lens L12 each having a convex surface facing the object is arranged. As the second lens group G2, in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, a biconvex lens L23, and a negative meniscus lens L24 having a concave surface facing the object are arranged. As the third lens group G3, in order from the object, a positive meniscus lens L31 having a convex surface facing the object, a cemented lens formed by cementing a biconvex lens L32 and a biconcave lens L33, a biconcave lens L34, a biconvex lens 135, a biconvex lens L36, and a negative meniscus lens L37 having a concave surface facing the object are arranged. Moreover, each lens is arranged in such a manner that the conditional expression (11) (a corresponding value of the conditional expression (11) is 4.06) is satisfied.

According to the method for manufacturing the zoom optical system related to the second embodiment as described above, while the zoom optical system ZL is provided with the image blur correction mechanism, the zoom optical system ZL having high optical performance can be realized.

Next, a third embodiment will be described with reference to drawings. As shown in FIG. 1, a zoom optical system ZL according to the third embodiment is formed of, disposed in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

According to this configuration, size reduction of the lens barrel and securement of a sufficient zoom ratio in the wide-angle end state can be achieved.

The zoom optical system ZL according to the third embodiment moves the first lens group G1 to a direction of the object along an optical axis direction upon zooming from the wide-angle end state to the telephoto end state.

According to this configuration, a sufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the third embodiment, focusing is made by moving at least a part of the third lens group G3 along the optical axis direction.

According to this configuration, variations in aberration (for example, spherical aberration) upon focusing can be suppressed.

Then, under the configuration, the following conditional expression (17) is satisfied: 0.73<(−f2)/f3<2.00  (17)

where f2 denotes a focal length of the second lens group G2, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (17) specifies a proper ratio of the focal length of the second lens group G2 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (17).

If the ratio thereof is less than a lower limit of the conditional expression (17), refractive power of the second lens group G2 increases, correction of coma aberration and astigmatism in the wide-angle end state becomes difficult, and therefore such a case is not preferable.

An effect of the third embodiment can be ensured by setting the lower limit of the conditional expression (17) to 0.75.

If the ratio thereof is more than an upper limit of the conditional expression (17), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the upper limit of the conditional expression (17) to 1.20.

In the zoom optical system ZL according to the third embodiment, zooming is preferably made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3.

According to this configuration, while variations in spherical aberration and curvature of field upon zooming are suppressed, a sufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the third embodiment, the third lens group G3 is formed of, disposed in order from the object, a 3A lens group G3A and a 3B lens group G3B each having positive refractive power, in which focusing is preferably made by moving the 3A lens group G3A along the optical axis direction.

According to this configuration, variations in aberration (for example, spherical aberration) upon focusing can be suppressed.

The zoom optical system ZL according to the third embodiment preferably satisfies the following conditional expression (18): 1.00<f3A/f3<4.00  (18)

where f3A denotes a focal length of the 3A lens group G3A.

The conditional expression (18) specifies a proper ratio of the focal length of the 3A lens group G3A to the focal length of the third lens group G3. Successful optical performance upon focusing and size reduction of the optical system can be achieved by satisfying the conditional expression (18).

If the ratio thereof is less than a lower limit of the conditional expression (18), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the lower limit of the conditional expression (18) to 1.50.

If the ratio thereof is more than an upper limit of the conditional expression (18), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the upper limit of the conditional expression (18) to 3.50.

In the zoom optical system ZL according to the third embodiment, the 3A lens group G3A is preferably formed of a single lens.

According to this configuration, size reduction of a focusing mechanism can be achieved.

The zoom optical system ZL according to the third embodiment preferably satisfies the following conditional expression (19): 1.00<|f3B|/f3<5.00  (19)

where f3 denotes a focal length of the third lens group G3.

The conditional expression (19) specifies a proper ratio of the focal length of the 3B lens group to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (19).

If the ratio thereof is less than a lower limit of the conditional expression (19), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the lower limit of the conditional expression (19) to 1.20.

If the ratio thereof is more than an upper limit of the conditional expression (19), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the upper limit of the conditional expression (19) to 3.00.

In the zoom optical system ZL according to the third embodiment, at least a part of the 3B lens group G3B is preferably configured to be movable, as a vibration-proof lens group VR for correcting an image blur, so as to have a component in a direction perpendicular to the optical axis.

According to this configuration, successful optical performance upon correcting the image blur (vibration proofing) can be realized. Moreover, size reduction of an image blur correction mechanism, including the vibration-proof lens group VR, can be achieved.

In the zoom optical system ZL according to the third embodiment, the vibration-proof lens group VR preferably has negative refractive power.

According to this configuration, successful optical performance upon correcting the image blur (vibration proofing) can be realized.

The zoom optical system ZL according to the third embodiment preferably satisfies the following conditional expression (20): 2.00<|fvr|/f3<6.00  (20)

where fvr denotes a focal length of the vibration-proof lens group VR.

The conditional expression (20) specifies a proper ratio of the focal length of the vibration-proof lens group VR to the focal length of the third lens group G3. Successful optical performance upon correcting the image blur and size reduction of the optical system can be achieved by satisfying the conditional expression (20).

If the ratio thereof is less than a lower limit of the conditional expression (20), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the third embodiment can be ensured by setting the lower limit of the conditional expression (20) to 2.50.

If the ratio thereof is more than an upper limit of the conditional expression (20), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable. Moreover, refractive power of the vibration-proof lens group VR is reduced, and a shift amount upon correcting the image blur (vibration proofing) increases, and size reduction of the lens barrel becomes difficult.

The effect of the third embodiment can be ensured by setting the upper limit of the conditional expression (20) to 4.00.

In the zoom optical system ZL according to the third embodiment, the vibration-proof lens group VR is preferably formed of a single lens.

According to this configuration, size reduction of the image blur correction mechanism can be achieved.

The zoom optical system ZL according to the third embodiment has a stop S, and the stop S preferably moves along the optical axis direction integrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can be simplified, and size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the third embodiment has a stop S, and the stop S is preferably arranged between the second lens group G2 and the image surface I.

According to this configuration, curvature of field and astigmatism can be successfully corrected.

The zoom optical system ZL according to the third embodiment preferably satisfies the following conditional expression (21): 30.00°<ωw<80.00°  (21)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (21) represents a condition specifying a value of an angle of view in the wide-angle end state. While the zoom optical system ZL has a wide angle of view, coma aberration, distortion, and curvature of field can be successfully corrected by satisfying the conditional expression (21).

Further successful aberration correction can be made by setting a lower limit of the conditional expression (21) to 33.00°. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (21) to 36.00°.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (21) to 77.00°.

The zoom optical system ZL according to the third embodiment preferably satisfies the following conditional expression (22): 2.00<ft/fw<15.00  (22)

where ft denotes a focal length of the zoom optical system in the telephoto end state, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

The conditional expression (22) represents a condition specifying a ratio of the focal length of the zoom optical system in the telephoto end state to the focal length of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, a high zoom ratio can be obtained, and simultaneously spherical aberration and coma aberration can be successfully corrected by satisfying the conditional expression (22).

Further successful aberration correction can be made by setting the lower limit of the conditional expression (22) to 2.30. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (22) to 2.50. The effect of the third embodiment can be exhibited to a maximum by setting the lower limit of the conditional expression (22) to 2.70.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (22) to 10.00. Still further successful aberration correction can be made by setting the upper limit of the conditional expression (22) to 7.00.

According to the third embodiment as described above, the zoom optical system ZL having high optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoom optical system ZL will be described with reference to FIG. 17. The camera 1 is identical with the camera 1 in the first embodiment, and the configuration has been already described, and therefore the description herein is omitted.

As is known also from each Example described later, the zoom optical system ZL according to the third embodiment, mounted in the camera 1 as an imaging lens 2, has high optical performance by the characteristic lens configuration. Thus, according to the present camera 1, the imaging device having high optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL is mounted on a single-lens reflex camera that has a quick return mirror and observes the subject by a finder optical system, an effect similar to the effect of the camera 1 can be produced. Moreover, even when the above-mentioned zoom optical system ZL is mounted on a video camera, an effect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZL having the configuration will be generally described with reference to FIG. 20. First, each lens is arranged within a lens barrel in such a manner that a zoom optical system ZL is formed of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power (step ST310). At this time, each lens is arranged in such a manner that the first lens group G1 moves to a direction of an object along an optical axis direction upon zooming from a wide-angle end state to a telephoto end state (step ST320). Each lens is arranged in such a manner that focusing is made by moving at least a part of the third lens group G3 along the optical axis direction (step ST330). Moreover, each lens is arranged within the lens barrel in such a manner that at least the following conditional expression (17) is satisfied among the conditional expressions (step ST340): 0.73<(−f2)/f3<2.00  (17)

where f2 denotes a focal length of the second lens group G2, and

f3 denotes a focal length of the third lens group G3.

To take a lens arrangement according to the third embodiment as one example, as shown in FIG. 1, in order from an object, a cemented lens formed by cementing a negative meniscus lens L11 and a positive meniscus lens L12 each having a convex surface facing the object is arranged. As the second lens group G2, in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, a biconvex lens L23, and a negative meniscus lens L24 having a concave surface facing the object are arranged. As the third lens group G3, in order from the object, a positive meniscus lens L31 having a concave surface facing the object, a cemented lens formed by cementing a biconvex lens L32 and a biconcave lens L33, a biconcave lens L34, a biconvex L35, a biconvex lens L36, and a negative meniscus lens L37 having a concave surface facing the object are arranged. Moreover, each lens is arranged in such a manner that the conditional expression (17) (a corresponding value of the conditional expression (17) is 0.76) is satisfied.

According to the method for manufacturing the zoom optical system related to the third embodiment as described above, the zoom optical system ZL having has high optical performance can be realized.

Next, a fourth embodiment will be described with reference to drawings. As shown in FIG. 1, a zoom optical system ZL according to the fourth embodiment has, disposed in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

According to this configuration, size reduction of a lens barrel in the wide-angle end state can be achieved.

The zoom optical system ZL according to the fourth embodiment moves the first lens group G1 to a direction of the object along an optical axis direction upon zooming from a wide-angle end state to a telephoto end state.

According to this configuration, a sufficient zoom ratio can be ensured.

Then, under the configuration, the following conditional expressions (23) and (24) are satisfied: 0.14<fw/f1<0.26  (23) 0.77<fw/f3<1.05  (24)

where fw denotes a focal length of the zoom optical system in the wide-angle end state,

f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (23) specifies a proper ratio of the focal length of the zoom optical system in a wide-angle end state to the focal length of the first lens group G1. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (23).

If the ratio thereof is less than a lower limit of the conditional expression (23), refractive power of the first lens group G1 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

An effect of the fourth embodiment can be ensured by setting the lower limit of the conditional expression (23) to 0.15.

If the ratio thereof is more than an upper limit of the conditional expression (23), refractive power of the first lens group G1 increases, correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the upper limit of the conditional expression (23) to 0.25.

The conditional expression (24) specifies a proper ratio of the focal length of the zoom optical system in a wide-angle end state to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (24).

If the ratio thereof is less than a lower limit of the conditional expression (24), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lower limit of the conditional expression (24) to 0.80.

If the ratio thereof is more than an upper limit of the conditional expression (24), refractive power of the third lens group G3 increases, and correction of spherical aberration, coma aberration, and astigmatism becomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the upper limit of the conditional expression (24) to 1.02.

In the zoom optical system ZL according to the fourth embodiment, zooming is preferably made by varying an air distance between the first lens group G1 and the second lens group G2, an air distance between the second lens group G2 and the third lens group G3.

According to this configuration, while variations in spherical aberration and curvature of field upon zooming are suppressed, a sufficient zoom ratio can be ensured.

In the zoom optical system ZL according to the fourth embodiment, at least a part of the second lens group G2 or at least a part of the third lens group G3 is preferably configured to be movable, as a vibration-proof lens group for correcting an image blur (caused by camera shake or the like), so as to have a component in a direction perpendicular to the optical axis.

According to this configuration, size reduction of an image blur correction mechanism, including the vibration-proof lens group, can be achieved.

In the zoom optical system ZL according to the fourth embodiment, focusing is preferably made by moving at least a part of the third lens group G3 along the optical axis direction.

According to this configuration, variations in aberration (for example, spherical aberration) upon focusing can be suppressed.

In the zoom optical system ZL according to the fourth embodiment, the third lens group G3 is formed of, disposed in order from the object, a 31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33, and the 32nd lens group G32 is preferably configured to be movable, as a vibration-proof lens group, so as to have a component in a direction perpendicular to the optical axis.

According to this configuration, successful optical performance upon correcting the image blur (vibration proofing) can be realized. Moreover, size reduction of the image blur correction mechanism can be achieved.

In the zoom optical system ZL according to the fourth embodiment, the 32nd lens group G32 preferably has negative refractive power.

According to this configuration, successful optical performance upon correcting the image blur (vibration proofing) can be realized.

The zoom optical system ZL according to the fourth embodiment preferably satisfies the following conditional expression (25): 2.00<(−f32)/f3<6.00  (25)

where f32 denotes a focal length of the 32nd lens group G32, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (25) specifies a proper ratio of the focal length of the 32nd lens group G32 to the focal length of the third lens group G3. Successful optical performance upon correcting the image blur (vibration proofing) and size reduction of the optical system can be achieved by satisfying the conditional expression (25).

If the ratio thereof is less than a lower limit of the conditional expression (25), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lower limit of the conditional expression (25) to 2.50.

If the ratio thereof is more than an upper limit of the conditional expression (25), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult. Moreover, refractive power of the 32nd lens group G32 is reduced and a shift amount upon correcting the image blur (vibration proofing) increases, and size reduction of the lens barrel becomes difficult.

The effect of the fourth embodiment can be ensured by setting the upper limit of the conditional expression (25) to 4.00.

The zoom optical system ZL according to the fourth embodiment preferably satisfies the following conditional expression (26): 0.50<|f31|/f3<2.00  (26)

where f31 denotes a focal length of the 31st lens group G31, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (26) specifies a proper ratio of the focal length of the 31st lens group G31 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (26).

If the ratio thereof is less than a lower limit of the conditional expression (26), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lower limit of the conditional expression (26) to 0.70.

If the ratio thereof is more than an upper limit of the conditional expression (26), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the upper limit of the conditional expression (26) to 1.50.

The zoom optical system ZL according to the fourth embodiment preferably satisfies the following conditional expression (27): 1.00<|f33|/f3  (27)

where f33 denotes a focal length of the 33rd lens group G33, and

f3 denotes a focal length of the third lens group G3.

The conditional expression (27) specifies a proper ratio of the focal length of the 33rd lens group G33 to the focal length of the third lens group G3. Successful optical performance and size reduction of the optical system can be achieved by satisfying the conditional expression (27).

If the ratio thereof is less than a lower limit of the conditional expression (27), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. If refractive power of the first lens group G1 and the second lens group G2 is increased in order to achieve size reduction, correction of coma aberration, astigmatism, and curvature of field becomes difficult, and therefore such a case is not preferable.

The effect of the fourth embodiment can be ensured by setting the lower limit of the conditional expression (27) to 2.00.

In the zoom optical system ZL according to the fourth embodiment, the 32nd lens group G32 is preferably configured of a single lens.

According to this configuration, variations in decentering coma aberration and variations in curvature of field upon correcting the image blur can be successfully corrected. Moreover, size reduction of the image blur correction mechanism can be achieved.

In the zoom optical system 1ZL according to the fourth embodiment, the 31st lens group G31 is preferably formed of, disposed in order from the object, a front group G3F having positive refractive power and a rear group G3R, in which focusing is preferably made by moving the front group G3F along the optical axis direction.

According to this configuration, variations in aberration (for example, spherical aberration) upon focusing can be suppressed.

The zoom optical system ZL according to the fourth embodiment has a stop S, and the stop S preferably moves along the optical axis direction integrally with the third lens group G3 upon zooming.

According to this configuration, lens barrel structure can be simplified, and size reduction of the lens barrel can be achieved.

The zoom optical system ZL according to the fourth embodiment has a stop S, and the stop S is preferably arranged between the second lens group G2 and the image surface I.

According to this configuration, curvature of field and astigmatism can be successfully corrected.

The zoom optical system ZL according to the fourth embodiment preferably satisfies the following conditional expression (28): 30.00°<ωw<80.00°  (28)

where ωw denotes a half angle of view in a wide-angle end state.

The conditional expression (28) represents a condition specifying a value of an angle of view in the wide-angle end state. While the zoom optical system ZL has a wide angle of view, coma aberration, distortion, and curvature of field can be successfully corrected by satisfying the conditional expression (28).

Further successful aberration correction can be made by setting a lower limit of the conditional expression (28) to 33.00°. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (28) to 36.00°.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (28) to 77.00°.

The zoom optical system ZL according to the fourth embodiment preferably satisfies the following conditional expression (29): 2.00<ft/fw<15.00  (29)

where ft denotes a focal length of the zoom optical system in the telephoto end state, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

The conditional expression (29) represents a condition specifying a ratio of the focal length of the zoom optical system in the telephoto end state to the focal length of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, a high zoom ratio can be obtained, and simultaneously spherical aberration and coma aberration can be successfully corrected by satisfying the conditional expression (29).

Further successful aberration correction can be made by setting a lower limit of the conditional expression (29) to 2.30. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (29) to 2.50. The effect of the fourth embodiment can be exhibited to a maximum by setting the lower limit of the conditional expression (29) to 2.70.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (29) to 10.00. Still further successful aberration correction can be made by setting the upper limit of the conditional expression (29) to 7.00.

According to the fourth embodiment as described above, the zoom optical system ZL having high optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoom optical system ZL will be described with reference to FIG. 17. The camera 1 is identical with the camera 1 in the first embodiment, and the configuration has been already described above, and therefore the description herein is omitted.

As is known also from each Example described later, the zoom optical system ZL according to the fourth embodiment, mounted in the camera 1 as an imaging lens 2, has high optical performance by the characteristic lens configuration. Thus, according to the present camera 1, the imaging device having high optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL is mounted on a single-lens reflex camera that has a quick return mirror and observes the subject by a finder optical system, an effect similar to the effect of the camera 1 can be produced. Moreover, even when the above-mentioned zoom optical system ZL is mounted on a video camera, an effect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZL having the configuration will be generally described with reference to FIG. 21. First, each lens is arranged within a lens barrel in such a manner that the zoom optical system ZL has a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power (step ST410). At this time, each lens is arranged in such a manner that the first lens group G1 moves to a direction of an object along an optical axis direction upon zooming from a wide-angle end state to a telephoto end state (step ST420). Each lens is arranged within the lens barrel in such a manner that at least the following conditional expressions (23) and (24) are satisfied among the conditional expressions (step ST430): 0.14<fw/f1<0.26  (23) 0.77<fw/f3<1.05  (24)

where fw denotes a focal length of the zoom optical system in the wide-angle end state,

f1 denotes a focal length of the first lens group G1, and

f3 denotes a focal length of the third lens group G3.

To take a lens arrangement according to the fourth embodiment as one example, as shown in FIG. 1, as a first lens group G1, in order from an object, a cemented lens formed by cementing a negative meniscus lens L11 and a positive meniscus lens L12 each having a convex surface facing the object is arranged. As a second lens group G2, in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, a biconvex lens L23, and a negative meniscus lens L24 having a concave surface facing the object are arranged. As a third lens group G3, in order from the object, a positive meniscus lens L31 having a concave surface facing the object, a cemented lens formed by cementing a biconvex lens L32 and a biconcave lens L33, a biconcave lens L34, a biconvex L35, a biconvex lens L36, and a negative meniscus lens L37 having a concave surface facing the object are arranged. Moreover, each lens is arranged in such a manner that conditional expressions (23) and (24) (a corresponding value of the conditional expression (23) is 0.22 and a corresponding value of the conditional expression (24) is 0.90) are satisfied.

According to the method for manufacturing the zoom optical system according to the fourth embodiment as described above, the zoom optical system ZL having high optical performance can be obtained.

EXAMPLES ACCORDING TO FIRST TO FOURTH EMBODIMENTS

Next, each Example according to each of the first to fourth embodiments will be described based on drawings. Tables 1 to 4 are provided below, and these Tables indicate specifications in Examples 1 to 4, respectively.

However, Example 4 corresponds to only the second and fourth embodiments.

FIGS. 1, 5, 9, and 13 each are a cross-sectional drawing showing a configuration of each of zoom optical systems ZL (ZL 1 to ZL4) according to Examples 1, 2, 3, and 4. In these cross-sectional views showing the zoom optical systems ZL1 to ZL4, a moving track of each of lens groups along an optical axis upon zooming from a wide-angle end state (W) to a telephoto end state (T) is shown by an arrow.

Each reference sign for FIG. 1 according to Example 1 is independently used for each Example in order to avoid complication of the description by an increase in digit number of the reference sign. Therefore, even if reference signs common to reference signs in drawings according to other Examples are placed, the reference signs do not necessarily provide configurations common to the configurations in other Examples.

In each Example, a d-line (wavelength: 587.5620 nm) and a g-line (wavelength: 435.8350 nm) are selected as an object for calculation of aberration characteristics.

In “Lens Data” in the Table, a surface number indicates an order of optical surfaces from an object along a direction in which a ray of light progresses, r denotes a radius of curvature of each optical surface, D denotes a distance to the next lens surface being the distance on an optical axis from each optical surface to the next optical surface (or image surface), νd denotes the Abbe number of a material of an optical member on the basis of the d-line, and nd denotes a refractive index for the d-line of the material of the optical member. Moreover, (Variable) indicates a variable distance to the next lens surface, “∞” in a radius of curvature indicates a flat surface or an aperture, and (Stop S) indicates an aperture stop S. A refractive index (d-line) of air “1.000000” is omitted. When the optical surface is aspherical, “*” is placed on a left side of the surface number, and a paraxial radius of curvature is shown in a column of the radius of curvature r.

In “Aspherical Surface Data” in the Table, a shape of an aspherical surface shown in “Lens Data” is expressed by the following expression (a). Here, y denotes a height in a direction perpendicular to an optical axis, X(y) denotes an amount of displacement (amount of sag) in an optical axis direction at a height y, r denotes a radius of curvature (paraxial radius of curvature) of a reference spherical surface, κ denotes a conical coefficient, and An represents an n-th aspherical coefficient. In addition, “E-n” represents “×10^(−n),” and for example, “1.234E-05” represents “1.234×10⁻⁵.” X(y)=(y ² /r)/[1+{1−κ(y ² /r ²)}^(1/2)]+A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y ¹⁰  (a)

In “Various Data” in the Table, f denotes a focal length of a whole lens system, Fno denotes an F-number, ω denotes a half angle of view (a unit: °), Y denotes an image height, TL denotes a total length of a lens system (a distance from a lens forefront surface to an image surface I on an optical axis), and Bf denotes a back focus (a distance from a lens final surface to the image surface I on the optical axis).

In “Variable Distance Data” in the Table, a focal length f or imaging magnification β of a zoom optical system in a wide-angle end state, an intermediate focal length state, and a telephoto end state upon focusing on infinity and a short distant object (an imaging distance R=1.0 m), and a value of each variable distance is shown. In addition, DO denotes a distance from an object surface to a first surface, and Di (where, i is an integer) denotes a variable distance between an i-th surface and a (i+1)-th surface.

In “Lens Group Data” in the Table, a start surface number (surface number on a side closest to an object) of each group is shown in a group first surface, and a focal length of each group is shown in a group focal length.

In “Conditional Expression Corresponding Value” in the Table, values corresponding to the conditional expressions (1) to (29) are shown.

In the following, in all the values of the specifications, unless otherwise stated, “mm” is generally used for the focal length f, the radius of curvature r, the distance to the next lens surface D and other lengths, and the like entered therein. However, equivalent optical performance can be obtained even if the optical system is proportionally scaled up or scaled down, and therefore the values are not limited thereto. Moreover, the unit is not limited to “mm,” and other appropriate units can be used.

The description with regard to Table so far is common in all Examples, and the description in the following is omitted.

EXAMPLE 1

Example 1 will be described using FIG. 1, FIGS. 2A-2C, 3A-3C, 4A-4C and Table 1. As shown in FIG. 1, a zoom optical system ZL (ZL1) according to Example 1 is configured of, disposed in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

The first lens group G1 is configured of, disposed in order from the object, a cemented lens formed by cementing a negative meniscus lens L11 and a positive meniscus lens L12 each having a convex surface facing the object.

The second lens group G2 is configured of, disposed in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, a biconvex lens L23, and a negative meniscus lens L24 having a concave surface facing the object.

The third lens group G3 is configured of, disposed in order from the object, a 31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33.

The 31st lens group G31 is configured of, disposed in order from the object, a front group G3F having positive refractive power, and a rear group G3R. The front group G3F (focusing group) is configured of a positive meniscus lens L31 having a concave surface facing the object. The rear group G3R is configured of, disposed in order from the object, a cemented lens formed by cementing a biconvex lens L32 and a biconcave lens L33.

The 32nd lens group G32 (vibration-proof lens group) is configured of a biconcave lens L34. The 33rd lens group G33 is configured of, disposed in order from the object, a biconvex lens L35, a biconvex lens L36, and a negative meniscus lens L37 having a concave surface facing the object.

An aperture stop S determining an F-number is provided within the third lens group G3.

An image surface I is formed on an imaging element (not shown), and the imaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL1 according to Example 1, zooming from a wide-angle end state to a Telephoto end state is made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3. At this time, relative to the image surface I, the first lens group G1 monotonously moves to the object. The second lens group G2 moves along the optical axis so as to draw a convex track to an image. The third lens group G3 monotonously moves to the object. The aperture stop S monotonously moves to the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL1 according to Example 1, zooming from the wide-angle end state to the telephoto end state is made by moving each of the lens groups G1 to G3 along the optical axis in such a manner that the distance between the first lens group G1 and the second lens group G2 is enlarged, and the air distance between the second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL1 according to Example 1 has a configuration in which focusing is made by moving the front group G3F of the third lens group G3, namely the positive meniscus lens L31 having the concave surface facing the object, along the optical axis direction, and as shown by an arrow in FIG. 1, upon causing a change from a state of focusing on infinity to a state of focusing on the short distant object, the positive meniscus lens L31 moves from the object to the image.

Upon occurrence of an image blur, correction of the image blur (vibration proofing) on the image surface I is made by moving, as a vibration-proof lens group, the 32nd lens group G32, namely the biconcave lens L34 so as to have a component in a direction perpendicular to the optical axis.

Table 1 below shows values of each of specifications in Example 1. Surface numbers 1 to 25 in Table 1 correspond to optical surfaces m1 to m25 shown in FIG. 1, respectively.

TABLE 1 [Lens Data] Surface Number r D νd nd 1 41.994 1.800 23.80 1.846660 2 31.917 6.967 67.90 1.593190 3 1604.312 D3 (Variable) 4 79.168 1.500 32.35 1.850260 5 11.927 5.219 6 −52.994 1.000 42.73 1.834810 7 32.701 0.418 8 22.013 4.124 23.80 1.846660 9 −31.216 0.747 10 −21.084 1.000 42.73 1.834810 11 −79.290 D11 (Variable) 12 −459.370 1.607 49.62 1.772500 13 −32.039 D13 (Variable) 14 ∞ 2.000 (Stop S) 15 11.886 6.181 82.57 1.497820 16 −23.884 0.800 23.80 1.846660 17 297.976 2.028 18 −1480.750 0.800 49.62 1.772500 19 47.464 1.000 20 76.691 6.975 38.03 1.603420 21 −38.339 0.200 22 83.747 2.496 50.27 1.719990 23 −62.763 2.711 24 −9.776 1.000 42.73 1.834810 25 −16.921 Bf [Various Data] f 18.500 35.000 53.500 Fno 3.747 4.644 5.669 ω 39.556 21.350 14.391 Y 14.250 14.250 14.250 TL 88.166 99.495 109.353 Bf 17.445 26.392 35.677 [Variable Distance Data] (Infinity) (Imaging Distance 1 m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End End Intermediate End f, β 18.500 35.000 53.500 −0.0196 −0.0365 −0.0554 D0 0.000 0.000 0.000 911.8 900.5 890.6 D1 1.086 12.752 18.159 1.086 12.752 18.159 D11 15.129 5.845 1.011 15.637 6.644 2.065 D13 3.924 3.924 3.924 3.416 3.125 2.871 [Lens Group Data] Group Group First Group Focal Number Surface Length G1 1 83.101 G2 4 −15.594 G3 12 20.444 [Conditional Expression Corresponding Value] Conditional Expression(1): f1/(−f2) = 5.33 Conditional Expression(2): (−f32)/f3 = 2.91 Conditional Expression(3): |f31|/f3 = 1.02 Conditional Expression(4): |f33|/f3 = 3.59 Conditional Expression(5): ωw = 39.556 Conditional Expression(6): ft/fw = 2.89 Conditional Expression(7): f1/f3 = 4.06 Conditional Expression(8): (−f2)/f3 = 0.76 Conditional Expression(9): fw/f1 = 0.22 Conditional Expression(10): fw/f3 = 0.90 Conditional Expression(11): f1/f3 = 4.06 Conditional Expression(12): (−f32)/f3 = 2.91 Conditional Expression(13): |f31|/f3 = 1.02 Conditional Expression(14): |f33|/f3 = 3.59 Conditional Expression(15): ωw = 39.556 Conditional Expression(16): ft/fw = 2.89 Conditional Expression(17): (−f2)/f3 = 0.76 Conditional Expression(18): f3A/f3 = 2.18 Conditional Expression(19): |f3B|/f3 = 1.88 Conditional Expression(20): |fvr|/f3 = 2.91 Conditional Expression(21): ωw = 39.556 Conditional Expression(22): ft/fw = 2.89 Conditional Expression(23): fw/f1 = 0.22 Conditional Expression(24): fw/f3 = 0.90 Conditional Expression(25): (−f32)/f3 = 2.91 Conditional Expression(26): |f31|/f3 = 1.02 Conditional Expression(27): |f33|/f3 = 3.59 Conditional Expression(28): ωw = 39.556 Conditional Expression(29): ft/fw = 2.89

Table 1 shows that the zoom optical system ZL1 according to Example 1 satisfies the conditional expressions (1) to (29).

FIGS. 2A, 2B and 2C are graphs showing aberrations of the zoom optical system ZL1 according to Example 1 in a wide-angle end state (f=18.500), in which FIG. 2A is graphs showing various aberrations upon focusing on infinity, FIG. 2B is graphs showing various aberrations (imaging magnification β=−0.0196) upon focusing on a short distant object, and FIG. 2C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS. 3A, 3B and 3C are graphs showing aberrations of the zoom optical system ZL1 according to Example 1 in an intermediate focal length state (f=35.000), in which FIG. 3A is graphs showing various aberrations upon focusing on infinity, FIG. 3B is graphs showing various aberrations (imaging magnification β=−0.0365) upon focusing on a short distant object, and FIG. 3C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS. 4A, 4B and 4C are graphs showing aberrations of the zoom optical system ZL1 according to Example 1 in a telephoto end state (f=53.500), in which FIG. 4A is graphs showing various aberrations upon focusing on infinity, FIG. 4B is graphs showing various aberrations (imaging magnification β=−0.0554) upon focusing on a short distant object, and FIG. 4C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. In the present Example, as shown in FIG. 2C, FIG. 3C and FIG. 4C, optical performance upon vibration proofing is shown in graphs showing coma aberration, centering on an image height y=0.0, corresponding to image heights of vertically plus 10.0 and minus 10.0.

In each graph showing aberration, FNO denotes an F-number, NA denotes the number of apertures of a ray of light incident to the first lens group G1, A denotes an angle, namely a half angle (unit: °) of view of an entered ray of light, HO denotes an object height (unit: mm), Y denotes an image height, d denotes aberration in a d-line, and g denotes aberration in a g-line. A column without description of d or g aberration in the d-line. In the graphs showing spherical aberration, a solid line indicates spherical aberration and a broken line indicates sine conditions. In the graphs showing astigmatism, a solid line indicates a sagittal image surface and a broken line indicates a meridional image surface. In the graph showing coma aberration, a solid line indicates meridional coma. The description of the graphs showing aberration as described above is regarded to be the same also in other Examples, and the description thereof is omitted.

From each of the graphs showing aberration shown in FIGS. 2A-2C, 3A-3C and 4A-4C, the zoom optical system ZL1 according to Example 1 is found to have high imaging performance in which various aberrations are successfully corrected from the wide-angle end state to the telephoto end. Moreover, the zoom optical system ZL1 is found to have high imaging performance also upon correcting the image blur.

EXAMPLE 2

Example 2 will be described using FIG. 5, FIGS. 6A-6C, 7A-7C, 8A-8C and Table 2. As shown in FIG. 5, a zoom optical system ZL (ZL2) according to Example 2 is configured of, disposed in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

The first lens group G1 is configured of, disposed in order from the object, a cemented lens formed by cementing a negative meniscus lens L11 and a positive meniscus lens L12 each having a convex surface facing the object.

The second lens group G2 is configured of, disposed in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, a biconvex lens L23, and a negative meniscus lens L24 having a concave surface facing the object.

The third lens group G3 is configured of, disposed in order from the object, a 31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33.

The 31st lens group G31 is configured of, disposed in order from the object, a front group G3F having positive refractive power and a rear group G3R. The front group G3F (focusing group) is configured of a positive meniscus lens L31 having a concave surface facing the object. The rear group G3R is configured of, disposed in order from the object, a biconvex lens L32, and a negative meniscus lens L33 having a concave surface facing the object.

The 32nd lens group G32 (vibration-proof lens group) is configured of a negative meniscus lens L34 having a concave surface facing the object. The 33rd lens group G33 is configured of, disposed in order from the object, a biconvex lens L35, and a negative meniscus lens L36 having a concave surface facing the object.

An aperture stop S determining an F-number is provided within the third lens group G3.

An image surface I is formed on an imaging element (not shown), and the imaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL2 according to Example 2, zooming from a wide-angle end state to a telephoto end state is made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3. At this time, relative to the image surface I, the first lens group G1 monotonously moves to the object. The second lens group G2 monotonously moves to the object. The third lens group G3 monotonously moves to the object. The aperture stop S monotonously moves to the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL2 according to Example 2, zooming from the wide-angle end state to the telephoto end state is made by moving each of the lens groups G1 to G3 along the optical axis in such a manner that the air distance between the first lens group G1 and the second lens group G2 is enlarged, and the air distance between the second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL2 according to Example 2 has a configuration in which focusing is made by moving the front group G3F of the third lens group G3, namely the positive meniscus lens L31 having the concave surface facing the object along the optical axis direction, and as shown by an arrow in FIG. 5, upon causing a change from a state of focusing on infinity to a state of focusing on a short distant object, the positive meniscus lens L31 moves from the object to an image.

Upon occurrence of an image blur, correction of the image blur (vibration proofing) on the image surface I is made by moving, as a vibration-proof lens group, the 32nd lens group G32, namely the negative meniscus lens L34 having the convex surface facing the object so as to have a component in a direction perpendicular to the optical axis.

Table 2 below shows values of each of specifications in Example 2. Surface numbers 1 to 23 in Table 2 correspond to optical surfaces m1 to m23 shown in FIG. 5, respectively.

TABLE 2 [Lens Data] Surface Number r D νd nd 1 45.608 1.800 23.80 1.846660 2 33.721 6.519 67.90 1.593190 3 45648.551 D3 (Variable) 4 45.310 1.500 32.35 1.850260 5 11.154 5.514 6 −66.392 1.000 42.73 1.834810 7 28.177 0.200 8 19.025 4.190 23.80 1.846660 9 −36.189 0.897 10 −20.633 1.000 42.73 1.834810 11 −125.484 D11 (Variable) 12 −244.725 1.512 42.73 1.834810 13 −35.967 D13 (Variable) 14 ∞ 2.000 (Stop S) 15 11.692 7.246 82.57 1.497820 16 −15.635 0.800 23.80 1.846660 17 −55.007 2.028 18 119.072 0.800 55.52 1.696800 19 30.792 1.886 20 46.232 7.366 34.92 1.801000 21 −29.295 2.129 22 −9.299 1.000 35.72 1.902650 23 −17.109 Bf [Various Data] f 18.500 34.176 53.500 Fno 3.606 4.649 5.743 ω 38.474 21.695 14.318 Y 14.250 14.250 14.250 TL 84.418 96.972 109.393 Bf 17.330 26.452 35.995 [Variable Distance Data] (Infinity) (Imaging Distance 1 m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End End Intermediate End f, β 18.500 34.176 53.500 −0.0196 −0.0358 −0.0556 D0 0.000 0.000 0.000 915.6 903.0 890.6 D3 1.003 12.242 19.287 1.003 12.242 19.287 D11 12.973 5.166 1.000 13.423 5.869 1.977 D13 3.717 3.717 3.717 3.266 3.013 2.739 [Lens Group Data] Group Group First Group Focal Number Surface Length G1 1 89.519 G2 4 −14.853 G3 12 18.756 [Conditional Expression Corresponding Value] Conditional Expression(1): f1/(−f2) = 6.03 Conditional Expression(2): (−f32)/f3 = 3.19 Conditional Expression(3): |f31|/f3 = 1.00 Conditional Expression(4): |f33|/f3 = 8.00 Conditional Expression(5): ωw = 38.474 Conditional Expression(6): ft/fw = 2.89 Conditional Expression(7): f1/f3 = 4.77 Conditional Expression(8): (−f2)/f3 = 0.79 Conditional Expression(9): fw/f1 = 0.21 Conditional Expression(10): fw/f3 = 0.99 Conditional Expression(11): f1/f3 = 4.77 Conditional Expression(12): (−f32)/f3 = 3.19 Conditional Expression(13): |f31|/f3 = 1.00 Conditional Expression(14): |f33|/f3 = 8.00 Conditional Expression(15): ωw = 38.474 Conditional Expression(16): ft/fw = 2.89 Conditional Expression(17): (−f2)/f3 = 0.79 Conditional Expression(18): f3A/f3 = 2.68 Conditional Expression(19): |f3B|/f3 = 1.64 Conditional Expression(20): |fvr|/f3 = 3.19 Conditional Expression(21): ωw = 38.474 Conditional Expression(22): ft/fw = 2.89 Conditional Expression(23): fw/f1 = 0.21 Conditional Expression(24): fw/f3 = 0.99 Conditional Expression(25): (−f32)/f3 = 3.19 Conditional Expression(26): |f31|/f3 = 1.00 Conditional Expression(27): |f33|/f3 = 8.00 Conditional Expression(28): ωw = 38.474 Conditional Expression(29): ft/fw = 2.89

Table 2 shows that the zoom optical system ZL2 according to Example 2 satisfies the conditional expressions (1) to (29).

FIGS. 6A, 6B and 6C are graphs showing aberrations of the zoom optical system ZL2 according to Example 2 in a wide-angle end state (f=18.500), in which FIG. 6A is graphs showing various aberrations upon focusing on infinity, FIG. 6B is graphs showing various aberrations (imaging magnification β=−0.0196) upon focusing on a short distant object, and FIG. 6C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS. 7A, 7B and 7C are graphs showing aberrations of the zoom optical system ZL2 according to Example 2 in an intermediate focal length state (f=34.176), in which FIG. 7A is graphs showing various aberrations upon focusing on infinity, FIG. 7B is graphs showing various aberrations (imaging magnification β=−0.0358) upon focusing on a short distant object, and FIG. 7C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS. 8A, 8B and 8C are graphs showing aberrations of the zoom optical system ZL2 according to Example 2 in a telephoto end state (f=53.500), in which FIG. 8A is graphs showing various aberrations upon focusing on infinity, FIG. 8B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0556), and FIG. 8C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. In the present Example, as shown in FIG. 6C, FIG. 7C, and FIG. 8C, optical performance upon vibration proofing is shown in graphs showing coma aberration, centering on an image height y=0.0, corresponding to image heights of vertically plus 10.0 and minus 10.0.

From each of the graphs showing aberration shown in FIGS. 6A-6C, 7A-7C and 8A-8C, the zoom optical system ZL2 according to Example 2 is found to have high imaging performance in which various aberrations are successfully corrected from the wide-angle end state to the telephoto end. Moreover, the zoom optical system ZL2 is found to have high imaging performance also upon correcting the image blur.

EXAMPLE 3

Example 3 will be described using FIG. 9, FIGS. 10A-10C, 11A-11C, 12A-12C and Table 3. As shown in FIG. 9, a zoom optical system ZL (ZL3) according to Example 3 is configured of, disposed in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

The first lens group G1 is configured of, disposed in order from the object, a cemented lens formed by cementing a negative meniscus lens L11 having a convex surface facing the object and a biconvex lens L12.

The second lens group G2 is configured of, disposed in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, and a positive meniscus lens L23 having a convex surface facing the object. A surface of the negative meniscus lens L21 to the object is aspherical.

The third lens group G3 is configured of, disposed in order from the object, a 31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33.

The 31st lens group G31 is configured of, disposed in order from the object, a front group G3F having positive refractive power and a rear group G3R. The front group G3F (focusing group) is configured of a biconvex lens L31. The rear group G3R is configured of, disposed in order from the object, a cemented lens formed by cementing a biconvex L32 and a negative meniscus lens L33 having a concave surface facing the object.

The 32nd lens group G32 (vibration-proof lens group) is configured of a negative meniscus lens L34 having a convex surface facing the object. The 33rd lens group G33 is configured of, disposed in order from the object, a biconvex lens L35, and a negative meniscus lens L36 having a concave surface facing the object. A surface of the negative meniscus lens L34 to the object is aspherical. A surface of the negative meniscus lens L36 to the object is aspherical.

An aperture stop S determining an F-number is provided within the third lens group G3.

An image surface I is formed on an imaging element (not shown), and the imaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL3 according to Example 3, zooming from a wide-angle end state to a telephoto end state is made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3. At this time, relative to the image surface I, the first lens group G1 monotonously moves to the object. The second lens group G2 monotonously moves to the object. The third lens group G3 monotonously moves to the object. The aperture stop S monotonously moves to the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL3 according to Example 3, zooming from the wide-angle end state to the telephoto end state is made by moving each of the lens groups G1 to G3 along the optical axis in such a manner that the air distance between the first lens group G1 and the second lens group G2 is enlarged, and the air distance between the second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL3 according to Example 3 has a configuration in which focusing is made by moving the front group G3F of the third lens group G3, namely the biconvex lens L31 along the optical axis direction, and as shown by an arrow in FIG. 9, upon causing a change from a state of focusing on infinity to a state of focusing on short distant object, the biconvex lens L31 moves from the object to an image.

Upon occurrence of an image blur, correction of the image blur (vibration proofing) on the image surface I is made by moving, as a vibration-proof lens group, the 32nd lens group G32, namely the negative meniscus lens L34 having the convex surface facing the object so as to have a component in a direction perpendicular to the optical axis.

Table 3 below shows values of each of specifications in Example 3. Surface numbers 1 to 22 in Table 3 correspond to optical surfaces m1 to m22 shown in FIG. 9, respectively

TABLE 3 [Lens Data] Surface Number r D νd nd 1 54.753 1.500 23.80 1.846660 2 38.695 5.554 67.90 1.593190 3 −34295.201 D3 (Variable) *4 78.694 0.160 38.09 1.553890 5 98.152 1.200 42.73 1.834810 6 10.847 3.606 7 −970.417 1.000 42.73 1.834810 8 23.052 1.059 9 17.651 2.718 25.45 1.805180 10 124.240 D10 (Variable) 11 756.198 1.530 44.80 1.744000 12 −42.339 D12 (Variable) 13 ∞ 2.000 (Stop S) 14 10.744 4.744 82.57 1.497820 15 −14.187 0.800 32.35 1.850260 16 −36.052 2.298 *17 61.167 0.800 49.26 1.743200 18 25.724 3.680 19 40.116 2.998 36.40 1.620040 20 −27.927 2.317 *21 −8.706 1.000 31.27 1.903660 22 −17.386 Bf [Aspherical Surface Data] The 4th Surface κ = 1.0000 A4 = −8.92993E−06 A6 = −3.84277E−08 A8 = 5.03368E−10 A10 = −1.64069E−12 The 17th Surface κ = 1.0000 A4 = 4.87068E−06 A6 = −6.89267E−08 A8 = 0.00000E+00 A10 = 0.00000E+00 The 21st Surface κ = 1.0000 A4 = −3.24561E−05 A6 = −9.10280E−07 A8 = 2.25192E−08 A10 = −6.24358E−10 [Various Data] f 18.477 34.000 53.500 Fno 3.630 4.663 5.630 ω 39.444 21.946 14.295 Y 14.250 14.250 14.250 TL 74.395 88.467 104.339 Bf 17.318 26.476 34.918 [Variable Distance Data] (Infinity) (Imaging Distance 1 m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End End Intermediate End f, β 18.477 34.000 53.500 −0.0194 −0.0355 −0.0552 D0 0.000 0.000 0.000 925.6 911.5 895.7 D3 1.000 14.075 25.532 1.000 14.075 25.532 D10 13.187 5.026 1.000 13.679 5.760 2.066 D12 3.919 3.919 3.919 3.428 3.185 2.852 [Lens Group Data] Group Group First Group Focal Number Surface Length G1 1 110.968 G2 4 −16.768 G3 11 18.415 [Conditional Expression Corresponding Value] Conditional Expression(1): f1/(−f2) = 6.62 Conditional Expression(2): (−f32)/f3 = 3.28 Conditional Expression(3): |f31|/f3 = 0.93 Conditional Expression(4): |f33|/f3 = 7.37 Conditional Expression(5): ωw = 39.444 Conditional Expression(6): ft/fw = 2.90 Conditional Expression(7): f1/f3 = 6.03 Conditional Expression(8): (−f2)/f3 = 0.91 Conditional Expression(9): fw/f1 = 0.17 Conditional Expression(10): fw/f3 = 1.00 Conditional Expression(11): f1/f3 = 6.03 Conditional Expression(12): (−f32)/f3 = 3.28 Conditional Expression(13): |f31|/f3 = 0.93 Conditional Expression(14): |f33|/f3 = 7.37 Conditional Expression(15): ωw = 39.444 Conditional Expression(16): ft/fw = 2.90 Conditional Expression(17): (−f2)/f3 = 0.91 Conditional Expression(18): f3A/f3 = 2.93 Conditional Expression(19): |f3B|/f3 = 1.63 Conditional Expression(20): |fvr|/f3 = 3.28 Conditional Expression(21): ωw = 39.444 Conditional Expression(22): ft/fw = 2.90 Conditional Expression(23): fw/f1 = 0.17 Conditional Expression(24): fw/f3 = 1.00 Conditional Expression(25): (−f32)/f3 = 3.28 Conditional Expression(26): |f31|/f3 = 0.93 Conditional Expression(27): |f33|/f3 = 7.37 Conditional Expression(28): ωw = 39.444 Conditional Expression(29): ft/fw = 2.90

Table 3 shows that the zoom optical system ZL3 according to Example 3 satisfies the conditional expressions (1) to (29).

FIGS. 10A, 10B and 10C are graphs showing aberrations of the zoom optical system ZL3 according to Example 3 in a wide-angle end state (f=18.477), in which FIG. 10A is graphs showing various aberrations upon focusing on infinity, FIG. 10B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0194), and FIG. 10C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS. 11A, 11B and 11C are graphs showing aberrations of the zoom optical system ZL3 according to Example 3 in an intermediate focal length state (f=34.000), in which FIG. 11A is graphs showing various aberrations upon focusing on infinity, FIG. 11B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0355), and FIG. 11C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS. 12A, 12B and 12C are graphs showing aberrations of the zoom optical system ZL3 according to Example 3 in a telephoto end state (f=53.500), in which FIG. 12A is graphs showing various aberrations upon focusing on infinity, FIG. 12B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0552), and FIG. 12C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon the focusing on infinity. In the present Example, as shown in FIG. 10C, FIG. 11C and FIG. 12C, optical performance upon vibration proofing is shown in graphs showing coma aberration, centering on an image height y=0.0, corresponding to image heights of vertically plus 10.0 and minus 10.0.

From each of the graphs showing aberration shown in FIGS. 10A-10C, 11A-11C and 12A-12C, the zoom optical system ZL3 according to Example 3 is found to have high imaging performance in which various aberrations are successfully corrected from the wide-angle end state to the telephoto end. Moreover, the zoom optical system ZL3 is found to have high imaging performance also upon correcting the image blur.

EXAMPLE 4

Example 4 will be described using FIG. 13, FIGS. 14A-14C, 15A-15C, 16A-16C and Table 4. As shown in FIG. 13, a zoom optical system ZL (ZL4) according to Example 4 is configured of, disposed in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power.

The first lens group G1 is configured of, disposed in order from the object, a cemented lens formed by cementing a negative meniscus lens L11 having a convex surface facing the object, and a biconvex lens L12.

The second lens group G2 is configured of, disposed in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, and a positive meniscus lens L23 having a convex surface facing the object. A surface of the negative meniscus lens L21 to the object is aspherical.

The third lens group G3 is configured of, disposed in order from the object, a 31st lens group G31, a 32nd lens group G32, and a 33rd lens group G33.

The 31st lens group G31 is configured of, disposed in order from the object, a front group G3F having positive refractive power and a rear group G3R. The front group G3F (focusing group) is configured of a biconvex lens L31, The rear group G3R is configured of, disposed in order from the object, a cemented lens formed by cementing a biconvex lens L32 and a biconcave lens L33.

The 32nd lens group G32 (vibration-proof lens group) is configured of a negative meniscus lens L34 having a convex surface facing the object. The 33rd lens group G33 is configured of, disposed in order from the object, a biconvex lens L35 and a biconcave lens L36. A surface of the negative meniscus lens L36 to the object is aspherical.

The fourth lens group G4 is configured of a biconvex lens L41.

An aperture stop S determining an F-number is provided within the third lens group G3.

An image surface I is formed on an imaging element (not shown), and the imaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL4 according to Example 4, zooming from a wide-angle end state to a telephoto end state is made by varying an air distance between the first lens group G1 and the second lens group G2, an air distance between the second lens group G2 and the third lens group G3, and an air distance between the third lens group G3 and the fourth lens group G4. At this time, relative to the image surface I, the first lens group G1 monotonously moves to the object. The second lens group G2 monotonously moves to a direction of the object. The third lens group G3 monotonously moves to the object. The fourth lens group G4 monotonously moves to the object. The aperture stop S monotonously moves to the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL4 according to Example 4, zooming from the wide-angle end state to the telephoto end state is made by moving each of the lens groups G1 to G4 along the optical axis in such a manner that the air distance between the first lens group G1 and the second lens group G2 is enlarged, the air distance between the second lens group G2 and the third lens group G3 is reduced, and the air distance between the third lens group G3 and a fourth lens group G4 is enlarged.

The zoom optical system ZL4 according to Example 4 has a configuration in which focusing is made by moving the front group G3F of the third lens group G3, namely the biconvex lens L31 along the optical axis direction, and as shown by an arrow in FIG. 13, upon causing a change from a state of focusing on infinity to a state of focusing in a short distant object, the biconvex lens L31 moves from the object to an image.

Upon occurrence of an image blur, correction of the image blur (vibration proofing) on the image surface I is made by moving, as a vibration-proof lens group, the 32nd lens group G32, namely the negative meniscus lens L34 having the convex surface facing the object so as to have a component in a direction perpendicular to the optical axis.

Table 4 below shows values of each of specifications in Example 4. Surface numbers 1 to 23 in Table 4 correspond to optical surfaces m1 to m23 shown in FIG. 13, respectively.

TABLE 4 [Lens Data] Surface Number r D νd nd 1 67.912 1.500 42.73 1.834810 2 44.077 4.405 67.90 1.593190 3 −288.500 D3 (Variable) *4 33.454 1.200 42.73 1.834810 5 10.199 4.749 6 −36.627 1.000 50.27 1.719990 7 36.778 0.404 8 19.164 2.419 23.80 1.846660 9 95.617 D9 (Variable) 10 89.310 1.766 65.44 1.603000 11 −30.641 D11 (Variable) 12 ∞ 2.000 (Stop S) 13 9.587 3.001 58.54 1.612720 14 −1767.044 1.000 23.80 1.846660 15 20.932 2.301 16 151.332 1.699 82.57 1.497820 17 24.318 1.805 18 16.814 3.077 69.89 1.518600 19 −24.653 1.282 *20 −12.479 1.000 35.72 1.902650 21 194.680 D21(Variable) 22 41.253 2.502 23.80 1.846660 23 −90.972 Bf [Aspherical Surface Data] The 4th Surface κ = 1.0000 A4 = −1.31511E−05 A6 = −1.12654E−07 A8 = 7.35232E−10 A10 = −2.69203E−12 The 20th Surface κ = 1.0000 A4 = −1.69994E−04 A6 = −2.07858E−06 A8 = 6.76235E−09 A10 = −8.84176E−10 [Various Data] f 18.500 34.061 53.500 Fno 3.568 4.700 5.851 ω 39.495 21.888 14.364 Y 14.250 14.250 14.250 TL 74.382 87.897 104.318 Bf 17.380 27.437 37.937 [Variable Distance Data] (Infinity) (Imaging Distance 1 m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End End Intermediate End f, β 18.500 34.061 53.500 −0.0194 −0.0355 −0.0556 D0 0.000 0.000 0.000 925.6 912.1 895.7 D3 1.000 12.968 22.438 1.000 12.968 22.438 D9 14.194 5.413 1.000 14.671 6.042 1.837 D11 3.342 3.342 3.342 2.865 2.712 2.504 D21 1.346 1.617 2.481 1.346 1.617 2.481 [Lens Group Data] Group Group First Group Focal Number Surface Length G1 1 112.838 G2 4 −17.024 G3 10 20.227 G4 22 33.817 [Conditional Expression Corresponding Value] Conditional Expression(11): f1/f3 = 5.58 Conditional Expression(12): (−f32)/f3 = 2.89 Conditional Expression(13): |f31|/f3 = 0.92 Conditional Expression(14): |f33|/f3 = 2.97 Conditional Expression(15): ωw = 39.495 Conditional Expression(16): ft/fw = 2.89 Conditional Expression(23): fw/f1 = 0.16 Conditional Expression(24): fw/f3 = 0.91 Conditional Expression(25): (−f32)/f3 = 2.89 Conditional Expression(26): |f31|/f3 = 0.92 Conditional Expression(27): |f33|/f3 = 2.97 Conditional Expression(28): ωw = 39.495 Conditional Expression(29): ft/fw = 2.89

Table 4 shows that the zoom optical system ZL4 according to Example 4 satisfies the conditional expressions (11) to (16) and (23) to (28).

FIGS. 14A, 14B and 14C are graphs showing aberrations of the zoom optical system ZL4 according to Example 4 in a wide-angle end state (f=18.500), in which FIG. 14A is graphs showing various aberrations upon focusing on infinity, FIG. 14B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0194), and FIG. 14C is graphs showing coma aberration when an image blur is corrected (a correction angle θ: 30°) upon focusing on infinity. FIGS. 15A, 15B and 15C are graphs showing aberrations of the zoom optical system ZL4 according to Example 4 in an intermediate focal length state (f=34.061), in which FIG. 15A is graphs showing various aberrations upon focusing on infinity, FIG. 15B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0355), and FIG. 15C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. FIGS. 16A, 16B and 16C are graphs showing aberrations of the zoom optical system ZL4 according to Example 4 in a telephoto end state (f=53.500), in which FIG. 16A is graphs showing various aberrations upon focusing on infinity, FIG. 16B is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.0556), and FIG. 16C is graphs showing coma aberration when an image blur is corrected (a correction angle θ=0.30°) upon focusing on infinity. In the present example, as shown in FIG. 14C, FIG. 15C, and FIG. 16C, optical performance upon vibration proofing is shown in graphs showing coma aberration, centering on an image height y=0.0, corresponding to image heights of vertically plus 10.0 and minus 10.0.

From each of the graphs showing aberration shown in FIGS. 14A-14C, 15A-15C and 16A-16C, the zoom optical system ZL4 according to Example 4 is found to have high imaging performance in which various aberrations are successfully corrected from the wide-angle end state to the telephoto end. Moreover, the zoom optical system ZL4 is found to have high imaging performance also upon correcting the image blur.

According to each Example described above, while the zoom optical system is provided with an image blur correction mechanism, the zoom optical system has high optical performance can be realized.

In addition, each Example described above shows one specific example of the zoom optical system according to each of the first to fourth embodiments, and the zoom optical systems according to the first to fourth embodiments are not limited thereto. In the first to fourth embodiments, the following content can be appropriately adopted within the range in which the optical performance is not adversely affected.

In Examples using numerical values according to the first to fourth embodiments, a three-group configuration was shown. However, the present invention can also be applied to other configurations such as a four-group configuration. For example, a configuration in which a lens or lens group is added thereto on a side closest to the object, or a configuration is allowed in which a lens or lens group is added thereto on a side closest to the image. Moreover, the lens group represents a part which is separated by the air distances which change upon zooming or focusing and have at least one lens.

In the first to fourth embodiments, the zoom optical system may be formed into a focusing lens group in which focusing on an infinite distant object to a short distant object is made by moving a single lens group or a plurality of lens groups, or a partial lens group in the optical axis direction. The focusing lens group can also be applied to autofocusing, and is also suitable for a motor drive (using an ultrasonic motor, or the like) for autofocusing. In particular, at least a part of the third lens group G3 is preferably applied as the focusing lens group.

In the first to fourth embodiments, the zoom optical system may be formed into the vibration-proof lens group in which the image blur caused by camera shake is corrected by moving the lens group or the partial lens group so as to have the component in the direction perpendicular to the optical axis, or rotationally moving (swinging) the lens group or the partial lens group in an in-plane direction including the optical axis. In particular, at least a part of the third lens group G3 is preferably applied as the vibration-proof lens group.

In the first to fourth embodiments, a lens surface may be formed of a spherical surface or a flat surface, or formed of an aspherical surface. When the lens surface is spherical or flat, lens processing and assembly and adjustment are facilitated, and deterioration of optical performance by an error of the processing and assembly and adjustment can be prevented. Thus, such a case is preferable. Moreover, when the lens surface is aspherical, the aspherical surface may be any aspherical surface, including an aspherical surface by grinding, a glass mold aspherical surface in which glass is formed into an aspherical surface shape by using a mold, and a composite type aspherical surface in which a resin is formed into the aspherical surface shape on a surface of glass. Moreover, the lens surface may be formed into a diffraction surface, or the lens may be formed into a gradient index lens (GRIN lens) or a plastic lens.

In the first to fourth embodiments, the aperture stop S is preferably arranged in a neighborhood of the third lens group G3 or within the third lens group G3. However, a lens frame may be used as substitution for such a role without providing a member as the aperture stop.

In the first to fourth embodiments, an antireflection film having high transmittance in a wide wavelength range may be applied to each lens surface in order to reduce a flare and a ghost to achieve high optical performance with high contrast.

The zoom optical systems ZL according to the first to fourth embodiments each have a zoom ratio of about 2 to 7.

DESCRIPTION OF THE EMBODIMENTS (FIFTH AND SIXTH EMBODIMENTS)

Hereinafter, a fifth embodiment will be described with reference to drawings. As shown in FIG. 22, a zoom optical system ZL according to the fifth embodiment has, disposed in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

According to this configuration, size reduction of a lens barrel can be achieved and variations in aberration upon zooming can be successfully corrected.

Moreover, in the zoom optical system ZL, focusing is made by moving, as a focusing lens group, at least a part of the third lens group G3 (for example, a biconvex lens L31 in FIG. 22) along an optical axis direction.

According to this configuration, size reduction of the lens barrel can be achieved and variations in aberration (for example, spherical aberration, curvature of field, and the like) upon focusing can be successfully corrected.

Under the configuration, the zoom optical system ZL satisfies the following conditional expression (30): 0.90<f3/fw<1.50  (30)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in a wide-angle end state.

The conditional expression (30) specifies a ratio of the focal length f3 of the third lens group G3 to the focal length fw of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, size reduction of the lens barrel and successful optical performance can be realized by satisfying the conditional expression (30).

If the ratio thereof is more than an upper limit of the conditional expression (30), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. Refractive power of the first lens group G1 and the second lens group G2 is to be increased in order to achieve size reduction, and correction of coma aberration, astigmatism, and curvature of field becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (30), refractive power of the third lens group G3 increases, and correction of spherical aberration, coma aberration, and astigmatism becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (30) to 1.00.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (30) to 1.35.

In the zoom optical system ZL according to the fifth embodiment, zooming is preferably made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3.

According to this configuration, spherical aberration and curvature of field caused upon zooming can be successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, upon zooming from the wide-angle end state to the telephoto end state, the air distance between the first lens group G1 and the second lens group G2 is preferably enlarged, and the air distance between the second lens group G2 and the third lens group G3 is preferably reduced.

According to this configuration, spherical aberration and curvature of field caused upon zooming can be successfully corrected.

The zoom optical system ZL according to the fifth embodiment preferably satisfies the following conditional expression (31): 4.70<f1/f3<30.00  (31)

where f1 denotes a focal length of the first lens group G1.

The conditional expression (31) specifies a ratio of the focal length f1 of the first lens group G1 to the focal length f3 of the third lens group G3. In the present zoom optical system ZL, size reduction of the lens barrel and a predetermined zoom ratio can be realized by satisfying the conditional expression (31).

If the ratio thereof is more than an upper limit of the conditional expression (31), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (31), refractive power of the first lens group G1 increases, and correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (31) to 4.76.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (31) to 10.00.

The zoom optical system ZL according to the fifth embodiment preferably satisfies the following conditional expression (32): 0.60<(−f2)/f3<1.05  (32)

where f2 denotes a focal length of the second lens group G2.

The conditional expression (32) specifies a ratio of the focal length f3 of the third lens group G3 to the focal length f2 of the second lens group G2. In the present zoom optical system ZL, successful optical performance and a predetermined zoom ratio can be realized by satisfying the conditional expression (32).

If the ratio thereof is more than an upper limit of the conditional expression (32), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (32), refractive power of the second lens group G2 increases, and correction of coma aberration and astigmatism in the wide-angle end state becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (32) to 0.70.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (32) to 1.00.

The zoom optical system ZL according to the fifth embodiment preferably satisfies the following conditional expression (33): 5.20<f1/(−f2)<30.00  (33)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (33) specifies a ratio of the focal length f1 of the first lens group G1 to the focal length f2 of the second lens group G2. In the present zoom optical system ZL, successful optical performance and a predetermined zoom ratio can be realized by satisfying the conditional expression (33).

If the ratio thereof is more than an upper limit of the conditional expression (33), refractive power of the second lens group G2 increases, and correction of coma aberration and astigmatism in the wide-angle end state becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (33), refractive power of the first lens group G1 increases, and correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (33) to 5.30.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (33) to 10.00.

In the zoom optical system ZL according to the fifth embodiment, at least a part of the third lens group G3 (for example, a positive meniscus lens L34 having a convex surface facing the object in FIG. 22) is preferably configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to the optical axis.

According to this configuration, variations in curvature of field and variations in decentering coma aberration upon correcting the image blur can be simultaneously corrected.

In the zoom optical system ZL according to the fifth embodiment, the first lens group G1 is preferably formed of one cemented lens.

According to this configuration, while size reduction of the lens barrel is achieved, lateral chromatic aberration in the telephoto end state can be successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, the second lens group G2 is preferably formed of two negative lenses and one positive lens.

According to this configuration, coma aberration and curvature of field in the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, the second lens group G2 is preferably formed of, disposed in order from the object, a negative lens, a negative, lens, and a positive lens.

According to this configuration, coma aberration and curvature of field in the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the fifth embodiment, the third lens group G3 is preferably formed of six or more lenses.

According to this configuration, spherical aberration and coma aberration can be successfully corrected.

The zoom optical system ZL according to the fifth embodiment preferably satisfies the following conditional expression (34): 30.00°<ωw<80.00°  (34)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (34) represents a condition specifying a value of an angle of view in the wide-angle end state. While the zoom optical system ZL has a wide angle of view, coma aberration, distortion, and curvature of field can be successfully corrected by satisfying the conditional expression (34).

Further successful aberration correction can be made by setting a lower limit of the conditional expression (34) to 33.00°. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (34) to 36.00°.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (34) to 77.00°.

The zoom optical system ZL according to the fifth embodiment preferably satisfies the following conditional expression (35): 2.00<ft/fw<15.00  (35)

where ft denotes a focal length of the zoom optical system in the telephoto end state.

The conditional expression (35) represents a condition specifying a ratio of the focal length of the zoom optical system in the telephoto end state to the focal length of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, a high zoom ratio can be obtained, and simultaneously spherical aberration and coma aberration can be successfully corrected by satisfying the conditional expression (35).

Further successful aberration correction can be made by setting a lower limit of the conditional expression (35) to 2.30. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (35) to 2.50. An effect of the fifth embodiment can be exhibited to a maximum by setting the lower limit of the conditional expression (35) to 2.70.

Further successful aberration correction can be made by setting an upper limit of the conditional expression (35) to 10.00. Still further successful aberration correction can be made by setting the upper limit of the conditional expression (35) to 7.00.

As shown in FIG. 22 and FIG. 26, in the zoom optical system ZL according to the fifth embodiment, a focusing lens group is preferably arranged, in the third lens group G3, on a side closer to the object than the vibration-proof lens group. At this time, the focusing lens group is preferably arranged, in the third lens group G3, on a side closest to the object. Moreover, the focusing lens group is preferably formed of a single lens.

As shown in FIG. 30, in the zoom optical system ZL according to the fifth embodiment, the vibration-proof lens group is preferably arranged, in the third lens group G3, on a side closer to the object than the focusing lens group. At this time, the vibration-proof lens group is preferably arranged, in the third lens group G3, on a side closest to the object. Moreover, the vibration-proof lens group is preferably formed of a single lens.

According to the fifth embodiment as described above, the zoom optical system ZL having successful optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoom optical system ZL will be described with reference to FIG. 34. As shown in FIG. 34, the camera 1 is a lens interchangeable camera (so-called mirrorless camera) provided with the above-mentioned zoom optical system ZL as an imaging lens 2.

In the camera 1, light from an object (subject) (not shown) is collected by the imaging lens 2 to form a subject image on an imaging surface of an imaging unit 3 through an OLPF (optical low pass filter) (not shown). The subject image is then subjected to photoelectric conversion by a photoelectric conversion element provided in the imaging unit 3 to produce an image of the subject. This image is displayed on an EVF (electronic view finder) 4 provided in the camera 1. Thus, a photographer can observe the subject through the EVF 4.

Moreover, if a release bottom (not shown) is pressed by the photographer, the image of the subject produced in the imaging unit 3 is stored in a memory (not shown). Thus, the photographer can photograph the subject by the camera 1.

As is known also from each Example described later, the zoom optical system ZL according to the fifth embodiment, mounted in the camera 1 as the imaging lens 2, has successful optical performance by the characteristic lens configuration. Thus, according to the present camera 1, the imaging device having successful optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL is mounted on a single-lens reflex camera that has a quick return mirror and observes the subject by a finder optical system, an effect similar to the effect of the camera 1 can be produced. Moreover, even when the above-mentioned zoom optical system ZL is mounted on a video camera, an effect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZL having the configuration will be generally described with reference to FIG. 35. First, each lens is arranged within a lens barrel in such a manner that a zoom optical system ZL has a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power (step ST510). At this time, each lens is arranged within the lens barrel in such a manner that focusing is made by moving at least a part of the third lens group G3 along an optical axis direction as a focusing lens group (step ST520). Each lens is arranged within the lens barrel in such a manner that at least the following conditional expression (30) is satisfied among the conditional expressions (step ST530): 0.90<f3/fw<1.50  (30)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

To take a lens arrangement according to the fifth embodiment as one example, as shown in FIG. 22, as the first lens group G1, in order from the object, a cemented positive lens formed by cementing a negative meniscus lens L11 having a convex surface facing the object and a biconvex lens L12 is arranged. As the second lens group G2, in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, and a positive meniscus lens L23 having a convex surface facing the object are arranged. As the third lens group G3, in order from the object, a biconvex lens L31, a cemented positive lens formed by cementing a biconvex lens L32 and a biconcave lens L33, a positive meniscus lens L34 having a convex surface facing the object, a biconvex lens L35, and a negative meniscus lens L36 having a convex surface facing the image are arranged. Moreover, each lens is arranged in such a manner that the conditional expression (30) (a corresponding value of the conditional expression (30) is 1.14) is satisfied.

In addition, in the manufacturing method, each lens is preferably arranged within the lens barrel in such a manner that at least apart of the third lens group G3 (for example, the positive meniscus lens L34 having the convex surface facing the object in FIG. 22) is movable, as a vibration-proof lens group for correcting the image blur, so as to have a component in a direction perpendicular to the optical axis.

Moreover, in the manufacturing method, each lens is preferably arranged within the lens barrel in such a manner that the focusing lens group is arranged, in the third lens group G3, on a side closer to the object than the vibration-proof lens group (see FIG. 22 and FIG. 26).

Moreover, in the manufacturing method, each lens is preferably arranged within the lens barrel in such a manner that the vibration-proof lens group is arranged, in the third lens group G3, on a side closer to the object than the focusing group (see FIG. 30).

According to the method for manufacturing the zoom optical system related to the fifth embodiment as described above, the zoom optical system ZL having successful optical performance can be obtained.

Next, a sixth embodiment will be described with reference to drawings. As shown in FIG. 22, a zoom optical system ZL according to the sixth embodiment has, disposed in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

According to this configuration, size reduction of the lens barrel can be realized and variations in aberration upon zooming can be successfully corrected.

Moreover, the zoom optical system ZL has a configuration in which at least a part of the third lens group G3 (for example, the positive meniscus lens L34 having the convex surface facing the object in FIG. 22) is movable, as a vibration-proof lens group for correcting the image blur, so as to have a component in a direction perpendicular to the optical axis.

According to this configuration, variations in curvature of field and variations in decentering coma upon correcting the image blur can be simultaneously corrected.

Under the configuration, the zoom optical system ZL satisfies the following conditional expression (36): 0.60<f3/fw<3.50  (36)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in a wide-angle end state.

The conditional expression (36) specifies a ratio of the focal length f3 of the third lens group G3 to the focal length fw of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, size reduction of the lens barrel and successful optical performance can be realized by satisfying the conditional expression (36).

If the ratio thereof is more than an upper limit of the conditional expression (36), refractive power of the third lens group G3 is reduced, and size reduction of the lens barrel becomes difficult. Refractive power of the first lens group G1 and the second lens group G2 is to be increased in order to achieve size reduction, and correction of coma aberration, astigmatism, and curvature of field becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (36), refractive power of the third lens group G3 increases, and correction of spherical aberration, coma aberration, and astigmatism becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (36) to 0.75. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (36) to 0.85.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (36) to 2.00. Still further successful aberration correction can be made by setting the upper limit of the conditional expression (36) to 1.50.

In the zoom optical system ZL according to the sixth embodiment, zooming is preferably made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3.

According to this configuration, spherical aberration and curvature of field caused upon zooming can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, upon zooming from the wide-angle end state to the telephoto end state, the air distance between the first lens group G1 and the second lens group G2 is preferably enlarged, and the air distance between the second lens group G2 and the third lens group G3 is preferably reduced.

According to this configuration, spherical aberration and curvature of field caused upon zooming can be successfully corrected.

The zoom optical system ZL according to the sixth embodiment preferably satisfies the following conditional expression (37): 4.70<f1/f3<30.00  (37)

where f1 denotes a focal length of the first lens group G1.

The conditional expression (37) specifies a ratio of the focal length f1 of the first lens group G1 to the focal length f3 of the third lens group G3. In the present zoom optical system, ZL size reduction of the lens barrel and a predetermined zoom ratio can be realized by satisfying the conditional expression (37).

If the ratio thereof is more than an upper limit of the conditional expression (37), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (37), refractive power of the first lens group G1 increases, and correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (37) to 4.76.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (37) to 10.00.

The zoom optical system ZL according to the sixth embodiment preferably satisfies the following conditional expression (38): 0.60<(−f2)/f3<1.05  (38)

where f2 denotes a focal length of the second lens group G2.

The conditional expression (38) specifies a ratio of the focal length f3 of the third lens group G3 to the focal length f2 of the second lens group G2. In the present zoom optical system ZL, successful optical performance and a predetermined zoom ratio can be realized by satisfying the conditional expression (38).

If the ratio thereof is more than an upper limit of the conditional expression (38), refractive power of the third lens group G3 increases, and correction of spherical aberration and coma aberration in the telephoto end state becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (38), refractive power of the second lens group G2 increases, and correction of coma aberration and astigmatism in the wide-angle end state becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (38) to 0.70.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (38) to 1.00.

The zoom optical system ZL according to the sixth embodiment preferably satisfies the following conditional expression (39): 5.20<f1/(−f2)<30.00  (39)

where f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (39) specifies a ratio of the focal length f1 of the first lens group G1 to the focal length f2 of the second lens group G2. In the present zoom optical system ZL, successful optical performance and a predetermined zoom ratio can be realized by satisfying the conditional expression (39).

If the ratio thereof is more than an upper limit of the conditional expression (39), refractive power of the second third lens group G2 increases, and correction of coma aberration and astigmatism in the wide-angle end state becomes difficult. If the ratio thereof is less than a lower limit of the conditional expression (39), refractive power of the first lens group G1 increases, and correction of coma aberration, astigmatism, and curvature of field in the telephoto end state becomes difficult.

Further successful aberration correction can be made by setting the lower limit of the conditional expression (39) to 5.30.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (39) to 10.00.

In the zoom optical system ZL according to the sixth embodiment, focusing is preferably made by moving at least a part of the third lens group G3 (for example, the biconvex lens L31 in FIG. 22) along the optical axis direction.

According to this configuration, size reduction of the lens barrel can be achieved and variations in aberration (for example, spherical aberration, curvature of field, and the like) upon focusing can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, the first lens group G1 is preferably formed of one cemented lens.

According to this configuration, while size reduction of the lens barrel is achieved, lateral chromatic aberration in the telephoto end state can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, the second lens group G2 is preferably formed of two negative lenses and one positive lens.

According to this configuration, coma aberration and curvature of field in the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, the second lens group G2 is preferably formed of, disposed in order from the object, a negative lens, a negative lens, and a positive lens.

According to this configuration, coma aberration and curvature of field in the wide-angle end state can be successfully corrected.

In the zoom optical system ZL according to the sixth embodiment, the third lens group G3 is preferably formed of six or more lenses.

According to this configuration, spherical aberration and coma aberration can be successfully corrected.

The zoom optical system ZL according to the sixth embodiment preferably satisfies the following conditional expression (40): 30.00°<ωw<80.00°  (40)

where ωw denotes a half angle of view in the wide-angle end state.

The conditional expression (40) represents a condition specifying a value of an angle of view in the wide-angle end state. While the zoom optical system ZL has a wide angle of view, coma aberration, distortion, and curvature of field can be successfully corrected by satisfying the conditional expression (40).

Further successful aberration correction can be made by setting the lower limit of the conditional expression (40) to 33.00°. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (40) to 36.00°.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (40) to 77.00°.

The zoom optical system ZL according to the sixth embodiment preferably satisfies the following conditional expression (41): 2.00<ft/fw<15.00  (41)

where ft denotes a focal length of the zoom optical system in the telephoto end state.

The conditional expression (41) represents a condition specifying a ratio of the focal length of the zoom optical system in the telephoto end state to the focal length of the zoom optical system in the wide-angle end state. In the present zoom optical system ZL, a high zoom ratio can be obtained, and simultaneously spherical aberration and coma aberration can be successfully corrected by satisfying the conditional expression (41).

Further successful aberration correction can be made by setting the lower limit of the conditional expression (41) to 2.30. Still further successful aberration correction can be made by setting the lower limit of the conditional expression (41) to 2.50. An effect of the sixth embodiment can be exhibited to a maximum by setting the lower limit of the conditional expression (41) to 2.70.

Further successful aberration correction can be made by setting the upper limit of the conditional expression (41) to 10.00. Still further successful aberration correction can be made by setting the upper limit of the conditional expression (41) to 7.00.

According to the sixth embodiment as described above, the zoom optical system ZL having successful optical performance can be realized.

Next, a camera (imaging device) 1 provided with the above-mentioned zoom optical system ZL will be described with reference to FIG. 34. The camera 1 is identical with the camera 1 in the fifth embodiment, and the configuration has been already described above, and therefore the description herein is omitted.

As is known also from each Example described later, the zoom optical system ZL according to the sixth embodiment, mounted in the camera 1 as an imaging lens 2, has successful optical performance by the characteristic lens configuration. Thus, according to the present camera 1, the imaging device having successful optical performance can be realized.

In addition, even when the above-mentioned zoom optical system ZL is mounted on a single-lens reflex camera that has a quick return mirror and observes the subject by a finder optical system, an effect similar to the effect of the camera 1 can be produced. Moreover, even when the above-mentioned zoom optical system ZL is mounted on a video camera, an effect similar to the effect of the camera 1 can be produced.

Subsequently, a method for manufacturing the zoom optical system ZL having the configuration will be generally described with reference to FIG. 36. First, each lens is arranged within a lens barrel in such a manner that a zoom optical system ZL has, disposed in order from an object, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power (step ST610). At this time, at least a part of the third lens group G3 is configured to be movable, as a vibration-proof lens group for correcting an image blur, so as to have a component in a direction perpendicular to an optical axis (step ST620). Each lens is arranged within the lens barrel in such a manner that at least the following conditional expression (36) is satisfied among the conditional expressions (step ST630): 0.60<f3/fw<3.50  (36)

where f3 denotes a focal length of the third lens group G3, and

fw denotes a focal length of the zoom optical system in the wide-angle end state.

To take a lens arrangement according to the sixth embodiment as one example, as shown in FIG. 22, as a first lens group G1, in order from an object, a cemented positive lens formed by cementing a negative meniscus lens L11 having a convex surface facing the object and a biconvex lens L12 is arranged. As a second lens group G2, in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, and a positive meniscus lens L23 having a convex surface facing the object are arranged. As a third lens group G3, in order from the object, a biconvex lens L31, a cemented positive lens formed by cementing a biconvex lens L32 and a biconcave lens L33, a positive meniscus lens L34 having a convex surface facing the object, a biconvex lens L35, and a negative meniscus lens L36 having a convex surface facing the image are arranged. Moreover, each lens is arranged in such a manner that the conditional expression (36) (a corresponding value of the conditional expression (36) is 1.14) is satisfied.

According to the method for manufacturing the zoom optical system related to the sixth embodiment as described above, the zoom optical system ZL having successful optical performance can be obtained.

EXAMPLES ACCORDING TO FIFTH AND SIXTH EMBODIMENTS

Next, each Example according to each of the fifth and sixth embodiments will be described based on drawings. Tables 5 to 7 are provided below, and these Tables show each of specifications in Examples 5 to 7.

FIG. 22, FIG. 26, and FIG. 30 each are a cross-sectional view showing a configuration of each of zoom optical systems ZL (ZL5 to ZL7) according to each Example. In the cross-sectional view of each of the zoom optical systems ZL5 to ZL7, a movement track of each of the lens groups G1 to G3 along the optical axis upon zooming from a wide-angle end state (W) to a telephoto end state (T) is shown by an arrow.

Each reference sign for FIG. 22 according to Example 5 is independently used for each Example in order to avoid complication of the description by an increase in digit number of the reference sign. Therefore, even if reference signs common to reference signs in drawings according to other Examples are placed, the reference signs do not necessarily provide configurations common to the configurations in other Examples.

In each Example, a d-line (wavelength: 587.5620 nm) and a g-line (wavelength: 435.8350 nm) are selected as an object for calculation of aberration characteristics.

In “Lens Data” in the Table, a surface number indicates an order of optical surfaces from the object along a direction in which a ray of light progresses, r denotes a radius of curvature of each optical surface, D denotes a distance to the next lens surface being the distance on an optical axis from each optical surface to the next optical surface (or image surface), νd denotes the Abbe number of a material of an optical member on the basis of the d-line, and nd denotes a refractive index for the d-line of the material of the optical member. Moreover, (Variable) indicates a variable distance to the next lens surface, “∞” in a radius of curvature indicates a flat surface or an aperture, and (Stop S) indicates an aperture stop S. A refractive index (d-line) of air “1.00000” is omitted. When the optical surface is aspherical, “*” is placed on a left side of the surface number, and a paraxial radius of curvature is shown in a column of the radius of curvature r.

In “Aspherical Surface Data” in the Table, a shape of an aspherical surface shown in “Lens Data” is expressed by the following expression (b). Here, y denotes a height in a direction perpendicular to an optical axis, X(y) denotes an amount of displacement (amount of sag) in an optical axis direction at a height y, r denotes a radius of curvature (paraxial radius of curvature) of a reference spherical surface, κ denotes a conical coefficient, and An represents an n-th aspherical coefficient. In addition, “E-n” represents “×10^(−n),” and for example, “1.234E-05” represents “1.234×10⁻⁵.” X(y)=(y ² /r)/[1+{1−κ(y ² /r ²)}^(1/2)]+A4×y ⁴ +A6×y ⁶ +A8×y ⁸ +A10×y ¹⁰  (b)

In “Various Data” in the Table, f denotes a focal length of a whole lens system, Fno denotes an F-number, ω denotes a half angle of view (a unit: °), Y denotes an image height, TL denotes a total length of a lens system (a distance from a lens forefront surface to an image surface I on an optical axis), and Bf denotes a back focus (a distance from a lens final surface to the image surface I on the optical axis).

In “Variable Distance Data” in the Table, a focal length f or imaging magnification β of a zoom optical system in a wide-angle end state, an intermediate focal length state, and a telephoto end state upon focusing on infinity and a short distant object (an imaging distance R=2.0 m), and a value of each variable distance is shown. In addition, DO denotes a distance from an object surface to a first surface, and Di (where, i is an integer) denotes a variable distance between an i-th surface and a (i+1)-th surface.

In “Lens Group Data” in the Table, a start surface number (surface number on a side closest to the object) of each group is shown in a group first surface, and a focal length of each group is shown in a group focal length.

In “Conditional Expression Corresponding Value” in the Table, values corresponding to the conditional expressions (30) to (41) are shown.

In the following, in all the values of the specifications, unless otherwise stated, “mm” is generally used for the focal length f, the radius of curvature r, the distance to the next lens surface D and other lengths, and the like entered therein. However, equivalent optical performance can be obtained even if the optical system is proportionally scaled up or scaled down, and therefore the values are not limited thereto. Moreover, the unit is not limited to “mm,” and other appropriate units can be used.

The description with regard to Table so far is common in all Examples, and the description in the following is omitted.

EXAMPLE 5

Example 5 will be described using FIG. 22, FIGS. 23A-23C, 24A-24C, 25A-25C and Table 5. As shown in FIG. 22, a zoom optical system ZL (ZL5) according to Example 5 is configured of, disposed in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

The first lens group G1 is formed of, disposed in order from the object, a cemented positive lens formed by cementing a negative meniscus lens L11 having a convex surface facing the object and a biconvex lens L12.

The second lens group G2 is formed of, disposed in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, and a positive meniscus lens L23 having a convex surface facing the object. A surface of the negative meniscus lens L21 to the object is aspherical.

The third lens group G3 is formed of, disposed in order from the object, a biconvex lens L31, a cemented positive lens formed by cementing a biconvex lens L32 and a biconcave lens L33, a positive meniscus lens L34 having a convex surface facing the object, a biconvex lens L35, and a negative meniscus lens L36 having a convex surface facing an image.

An aperture stop S determining an F-number is provided within the third lens group G3.

An image surface I is formed on an imaging element (not shown), and the imaging element is configured of a CCD or a CMOS, for example.

In the zoom optical system ZL5 according to Example 5, zooming from a wide-angle end state to a telephoto end state is made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3. At this time, relative to the image surface I, the first lens group G1 to the third lens group G3 move to the object. The aperture stop S moves to the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL5 according to Example 5, zooming from the wide-angle end state to the telephoto end state is made by moving each of the lens groups G1 to G3 along the optical axis in such a manner that the air distance between the first lens group G1 and the second lens group G2 is enlarged, and the air distance between the second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL5 according to Example 5 has a configuration in which focusing is made by moving the biconvex lens L31, in the third lens group G3, along the optical axis direction, and as shown by an arrow in FIG. 22, upon causing a change from a state of focusing on infinity to a state of focusing on a short distant object, the biconvex lens L31 moves from the object to the image.

Upon occurrence of an image blur, correction of the image blur (vibration proofing) on the image surface I is made by moving, as a vibration-proof lens group, the positive meniscus lens L34 having the convex surface facing the object in the third lens group G3 so as to have a component in a direction perpendicular to the optical axis.

Table 5 below shows values of each of specifications in Example 5. Surface numbers 1 to 21 in Table 5 correspond to optical surfaces m1 to m21 shown in FIG. 22, respectively.

TABLE 5 [Lens Data] Surface Number r D νd nd 1 73.1346 1.6000 23.80 1.84666 2 47.7461 4.4680 55.52 1.69680 3 −2795.9453 D3 (Variable) *4 86.1349 1.3000 46.60 1.80400 5 11.7958 6.0000 6 −86.9238 1.0000 46.60 1.80400 7 38.6168 0.1000 8 20.8772 3.0000 23.80 1.84666 9 111.9344 D9 (Variable) 10 32.7034 2.2000 55.35 1.67790 11 −64.0118 D11 (Variable) 12 ∞ 0.5000 (Stop S) 13 9.7190 3.1000 61.22 1.58913 14 −45.7099 1.1044 29.37 1.95000 15 14.5899 5.0000 16 30.0000 1.5000 31.27 1.90366 17 200.0000 3.0000 18 296.9316 2.1000 50.27 1.71999 19 −22.1475 1.6841 20 −9.9417 1.1000 46.60 1.80400 21 −24.7454 Bf (Variable) [Aspherical Surface Data] The 4th Surface κ = 1.0000 A4 = −1.68932E−06 A6 = 3.45601E−09 A8 = 3.25066E−11 A10 = −1.38349E−13 [Various Data] f 18.50~53.50 Fno 3.62~5.91 ω 39.30~14.42 Y 14.25~14.25 TL  80.892~108.569 Bf 18.519~37.340 [Variable Distance Data] (Infinity) (Imaging Distance 2 m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End End Intermediate End f, β 18.503 34.953 53.500 −0.009 −0.018 −0.027 D0 0.000 0.000 0.000 1918.427 1909.008 1890.749 D3 1.000 9.986 25.233 1.000 9.986 25.233 D9 17.878 6.525 2.500 18.261 6.878 3.013 D11 4.739 4.739 4.739 4.356 4.387 4.226 Bf 18.519 30.304 37.340 18.519 30.304 37.340 [Lens Group Data] Group Group First Group Focal Number Surface Length G1 1 114.802 G2 4 −18.462 G3 10 21.087 [Conditional Expression Corresponding Value] Conditional Expression(30): f3/fw = 1.14 Conditional Expression(31): f1/f3 = 5.44 Conditional Expression(32): f2/(−f3) = 0.88 Conditional Expression(33): f1/(−f2) = 6.22 Conditional Expression(34): ωw = 39.30 Conditional Expression(35): ft/fw = 2.89 Conditional Expression(36): f3/fw = 1.14 Conditional Expression(37): f1/f3 = 5.44 Conditional Expression(38): f2/(−f3) = 0.88 Conditional Expression(39): f1/(−f2) = 6.22 Conditional Expression(40): ωw = 39.30 Conditional Expression(41): ft/fw = 2.89

Table 5 shows that the zoom optical system ZL5 according to Example 5 satisfies the conditional expressions (30) to (41).

FIGS. 23A, 23B and 23C are graphs showing aberrations of the zoom optical system ZL5 according to Example 5 in a wide-angle end state (f=18.50), in which FIG. 23A is graphs showing various aberrations upon focusing on infinity, FIG. 23B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 23C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.009). FIGS. 24A, 24B and 24C are graphs showing aberrations of the zoom optical system ZL5 according to Example 5 in an intermediate focal length state (f=34.95), in which FIG. 24A is graphs showing various aberrations upon focusing on infinity, FIG. 24B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 24C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.018). FIGS. 25A, 25B and 25C are graphs showing aberrations of the zoom optical system ZL5 according to Example 5 in a telephoto end state (f=53.50), in which FIG. 25A is graphs showing various aberrations upon focusing on infinity, FIG. 25B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 25C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.027). In the present Example, as shown in FIG. 23B, FIG. 24B, and FIG. 25B, optical performance upon vibration proofing is shown in graphs showing coma aberration, centering on an image height y=0.0, corresponding to image heights of vertically plus 10.0 and minus 10.0.

In each graph showing aberration, FNO denotes an F-number, Y denotes an image height, d denotes aberration in a d-line, and g denotes aberration in a g-line. A column without description of d or g indicates aberration in the d-line. In the graphs showing spherical aberration, a value of the F-number corresponding to a maximum aperture is shown, and in the graphs showing astigmatism and distortion, a maximum value of the image height is shown. In the graphs showing astigmatism, a solid line indicates a sagittal image surface and a broken line indicates a meridional image surface. In the graphs showing coma aberration, a solid line indicates meridional coma, and a broken line indicates sagittal coma. The description of the graphs showing aberration above is regarded to be the same also in other Examples, and the description thereof is omitted.

From each of the graphs showing aberration shown in FIGS. 23A-23C, 24A-24C and 25A-25C, the zoom optical system ZL5 according to Example 5 is found to have high imaging performance in which various aberrations are successfully corrected from the wide-angle end state to the telephoto end state. Moreover, the zoom optical system ZL5 is found to have high imaging performance also upon correcting the image blur.

EXAMPLE 6

Example 6 will be described using FIG. 26, FIGS. 27A-27C, 28A-28C, 29A-29C and Table 6. As shown in FIG. 26, a zoom optical system ZL (ZL6) according to Example 6 is configured of, disposed in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

The first lens group G1 is formed of, disposed in order from the object, a cemented positive lens formed by cementing a negative meniscus lens L11 and a positive meniscus lens L12 each having a convex surface facing the object.

The second lens group G2 is formed of, disposed in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, and a positive meniscus lens L23 having a convex surface facing the object. A surface of the negative meniscus lens L21 to the object is aspherical.

The third lens group G3 is formed of, disposed in order from the object, a positive meniscus lens L31 having a convex surface facing the object, a cemented positive lens formed by cementing a biconvex lens L32 and a negative meniscus lens L33, a negative meniscus lens L34 having a convex surface facing the object, a biconvex lens L35, and a negative meniscus lens L36 having a convex surface facing an image. A surface of the negative meniscus lens L36 to the image is aspherical.

An aperture stop S determining an F-number is provided within the third lens group G3.

An image surface I is formed on an imaging element (not shown), and the imaging element is formed of a CCD or a CMOS, for example.

In the zoom optical system ZL6 according to Example 6, zooming from a wide-angle end state to a telephoto end state is made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3. At this time, relative to the image surface I, the first lens group G1 to the third lens group G3 move to the object. The aperture stop S moves to the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL6 according to Example 6, zooming from the wide-angle end state to the telephoto end state is made by moving each of the lens groups G1 to G3 along the optical axis in such a manner that the air distance between the first lens group G1 and the second lens group G2 is enlarged, and the air distance between the second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL6 according to Example 6 has a configuration in which focusing is made by moving the positive meniscus lens L31 having the convex surface facing the object, in the third lens group G3, along the optical axis direction, and as shown by an arrow in FIG. 26, upon causing a change from a state of focusing on infinity to a state of focusing on a short distant object, the positive meniscus lens L31 moves from the object to the image.

Upon occurrence of an image blur, correction of the image blur (vibration proofing) on the image surface I is made by moving, as a vibration-proof lens group, the negative positive meniscus lens L34 having the convex surface facing the object in the third lens group G3 so as to have a component in a direction perpendicular to the optical axis.

Table 6 below shows values of each of specifications in Example 6. Surface numbers 1 to 21 in Table 6 correspond to optical surfaces m1 to m21 shown in FIG. 26.

TABLE 6 [Lens Data] Surface Number r D νd nd 1 53.5681 1.6000 23.80 1.84666 2 37.0346 5.7211 55.52 1.69680 3 353.3821 D3 (Variable) *4 45.0000 1.2492 46.60 1.80400 5 12.0000 4.6255 6 −419.8499 1.0000 46.60 1.80400 7 16.0327 2.2223 8 17.7685 3.0523 23.80 1.84666 9 54.0639 D9 (Variable) 10 30.8461 2.0203 55.52 1.69680 11 1697.1702 D11 (Variable) 12 ∞ 0.5000 (Stop S) 13 15.5855 3.7128 63.88 1.51680 14 −13.3636 1.0121 27.57 1.75520 15 −31.5468 4.5348 16 52.8796 1.0000 29.37 1.95000 17 26.1372 4.8969 18 23.6866 2.7133 46.97 1.54072 19 −63.5925 1.9047 20 −10.9032 1.5000 46.60 1.80400 *21 −19.7349 Bf (Variable) [Aspherical Surface Data] The 4th Surface κ = 1.0000 A4 = −5.26610E−06 A6 = −3.69410E−08 A8 = 1.17750E−10 A10 = −9.98120E−14 The 21st Surface κ = 1.0000 A4 = 2.90520E−05 A6 = −1.19970E−08 A8 = −6.98280E−10 A10 = 0.00000E+00 [Various Data] f 18.74~52.08 Fno 3.77~5.71 ω 39.16~14.81 Y 14.25~14.25 TL 79.523~109.107 Bf 18.021~35.053 [Variable Distance Data] (Infinity) (Imaging Distance 2 m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End End Intermediate End f, β 18.741 34.496 52.082 −0.010 −0.018 −0.026 D0 0.000 0.000 0.000 1919.796 1906.950 1890.212 D3 1.546 11.351 25.190 1.546 11.351 25.190 D9 13.592 5.482 2.500 13.794 5.765 2.958 D11 3.099 3.099 3.099 2.897 2.816 2.641 Bf 18.021 29.172 35.053 18.021 29.172 35.053 [Lens Group Data] Group Group First Group Focal Number Surface Length G1 1 100.52307 G2 4 −15.10823 G3 10 19.34026 [Conditional Expression Corresponding Value] Conditional Expression(30): f3/fw = 1.03 Conditional Expression(31): f1/f3 = 5.20 Conditional Expression(32): f2/(−f3) = 0.78 Conditional Expression(33): f1/(−f2) = 6.65 Conditional Expression(34): ωw = 39.16 Conditional Expression(35): ft/fw = 2.78 Conditional Expression(36): f3/fw = 1.03 Conditional Expression(37): f1/f3 = 5.20 Conditional Expression(38): f2/(−f3) = 0.78 Conditional Expression(39): f1/(−f2) = 6.65 Conditional Expression(40): ωw = 39.16 Conditional Expression(41): ft/fw = 2.78

Table 6 shows that the zoom optical system ZL6 according to Example 6 satisfies the conditional expressions (30) to (41).

FIGS. 27A, 27B and 27C are graphs showing aberrations of the zoom optical system ZL6 according to Example 6 in a wide-angle end state (f=18.74), in which FIG. 27A is graphs showing various aberrations upon focusing on infinity, FIG. 27B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 27C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.010). FIGS. 28A, 28B and 28C are graphs showing aberrations of the zoom optical system ZL6 according to Example 6 in an intermediate focal length state (f=34.50), in which FIG. 28A is graphs showing various aberrations upon focusing on infinity, FIG. 28B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 28C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.018). FIGS. 29A, 29B and 29C are graphs showing aberrations of the zoom optical system ZL6 according to Example 6 in a telephoto end state (f=52.08), in which FIG. 29A is graphs showing various aberrations upon focusing on infinity, FIG. 29B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 29C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.026).

From each of the graphs showing aberration shown in FIGS. 27A-27C, 28A-28C and 29A-29C, the zoom optical system ZL6 according to Example 6 is found to have high imaging performance in which various aberrations are successfully corrected from the wide-angle end state to the telephoto end state. Moreover, the zoom optical system ZL6 is found to have high imaging performance also upon correcting the image blur.

EXAMPLE 7

Example 7 will be described using FIG. 30 to FIGS. 31A-31C, 32A-32C, 33A-33C and Table 7. As shown in FIG. 30, a zoom optical system ZL (ZL7) according to Example 7 is configured of, disposed in order from an object along an optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

The first lens group G1 is formed of, disposed in order from the object, a cemented positive lens formed by cementing a negative meniscus lens L11 having a convex surface facing the object and a biconvex lens L12.

The second lens group G2 is formed of, disposed in order from the object, a negative meniscus lens L21 having a convex surface facing the object, a biconcave lens L22, and a positive meniscus lens L23 having a convex surface facing the object. A surface of the negative meniscus lens L21 to the object is aspherical.

The third lens group G3 is formed of, disposed in order from the object, a positive meniscus lens L31 having a convex surface facing the object, a cemented positive lens formed by cementing a biconvex lens L32 and a negative meniscus lens L33 having a convex surface facing an image, a biconvex lens L34, and a biconcave lens L35. A surface of the negative meniscus lens L34 to the image is aspherical.

An aperture stop S determining an F-number is provided within the third lens group G3.

An image surface I is formed on an imaging element (not shown), and the imaging element is formed of a CCD or a CMOS, for example.

In the zoom optical system ZL7 according to Example 7, zooming from a wide-angle end state to a telephoto end state is made by varying an air distance between the first lens group G1 and the second lens group G2 and an air distance between the second lens group G2 and the third lens group G3. At this time, relative to the image surface I, the first lens group G1 to the third lens group G3 move to the object. The aperture stop S moves to the object integrally with the third lens group G3 upon zooming.

More specifically, in the zoom optical system ZL7 according to Example 7, zooming from the wide-angle end state to the telephoto end state is made by moving each of the lens groups G1 to G3 along the optical axis in such a manner that the air distance between the first lens group G1 and the second lens group G2 is enlarged, and the air distance between the second lens group G2 and the third lens group G3 is reduced.

The zoom optical system ZL7 according to Example 7 has a configuration in which focusing is made by moving the biconvex lens L34 of the third lens group G3 along an optical axis direction, and as shown by an arrow in FIG. 30, upon causing a change from a state of focusing on infinity to a state of focusing on a short distant object, the biconvex lens L34 moves from the object to the image.

Upon occurrence of an image blur, correction of the image blur (vibration proofing) on the image surface I is made by moving, as a vibration-proof lens group, the positive meniscus lens L31 having the convex surface facing the image in the third lens group G3 so as to have a component in a direction perpendicular to the optical axis.

Table 7 below shows values of each of specifications in Example 7. Surface numbers 1 to 19 in Table 7 correspond to optical surfaces m1 to m19 shown in FIG. 30.

TABLE 7 [Lens Data] Surface Number r D νd nd 1 53.2376 1.6000 23.80 1.84666 2 38.1514 6.3571 63.34 1.61800 3 −369.5355 D3 (Variable) *4 37.0679 1.2789 52.34 1.75500 5 11.0000 5.1524 6 −55.1564 1.0000 46.60 1.80400 7 24.6508 0.5019 8 17.1923 3.0456 23.80 1.84666 9 55.8429 D9 (Variable) 10 −147.8871 1.8235 59.42 1.58313 11 −38.8546 0.9660 12 ∞ 0.4673 (Stop S) 13 13.2618 3.3759 65.44 1.60300 14 −18.1264 1.0943 29.37 1.95000 15 −141.8073 D15 (Variable) 16 32.4435 1.9144 49.62 1.77250 *17 −28.4962 D17 (Variable) 18 −19.1230 1.1000 46.59 1.81600 19 55.1349 Bf (Variable) [Aspherical Surface Data] The 4th Surface κ = 1.0000 A4 = −2.53250E−05 A6 = −1.03610E−07 A8 = 7.17390E−10 A10 = −2.12490E−12 The 17th Surface κ = 1.0000 A4 = 7.38500E−05 A6 = 4.27730E−07 A8 = 0.00000E+00 A10 = 0.00000E+00 [Various Data] f 18.72~52.00 Fno 3.60~5.57 ω 39.22~14.29 Y 14.25~14.25 TL  74.332~95.718 Bf  18.038~32.068 [Variable Distance Data] (Infinity) (Imaging Distance 2 m) Wide-Angle Telephoto Wide-Angle Telephoto End Intermediate End End Intermediate End f, β 18.724 35.500 52.000 −0.010 −0.018 −0.027 D0 0.000 0.000 0.000 1924.987 1912.247 1903.600 D3 1.000 14.288 20.264 1.000 14.288 20.264 D9 13.907 5.856 2.000 13.907 5.856 2.000 D15 8.710 8.710 8.710 8.661 8.597 8.533 D17 3.000 3.000 3.000 3.049 3.112 3.177 Bf 18.038 25.541 32.068 18.038 25.541 32.068 [Lens Group Data] Group Group First Group Focal Number Surface Length G1 1 86.38416 G2 4 −15.99559 G3 10 17.86718 [Conditional Expression Corresponding Value] Conditional Expression(30): f3/fw = 0.95 Conditional Expression(31): f1/f3 = 4.83 Conditional Expression(32): f2/(−f3) = 0.90 Conditional Expression(33): f1/(−f2) = 5.40 Conditional Expression(34): ωw = 39.22 Conditional Expression(35): ft/fw = 2.78 Conditional Expression(36): f3/fw = 0.95 Conditional Expression(37): f1/f3 = 4.83 Conditional Expression(38): f2/(−f3) = 0.90 Conditional Expression(39): f1/(−f2) = 5.40 Conditional Expression(40): ωw = 39.22 Conditional Expression(41): ft/fw = 2.78

Table 7 shows that the zoom optical system ZL7 according to Example 7 satisfies the conditional expressions (30) to (41).

FIGS. 31A, 31B and 31C are graphs showing aberrations of the zoom optical system ZL7 according to Example 7 in a wide-angle end state (f=18.72), in which FIG. 31A is graphs showing various aberrations upon focusing on infinity, FIG. 31B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 31C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.010). FIGS. 32A, 32B and 32C are graphs showing aberrations of the zoom optical system ZL7 according to Example 7 in an intermediate focal length state (f=35.50), in which FIG. 32A is graphs showing various aberrations upon focusing on infinity, FIG. 32B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount=0.2 mm) upon focusing on infinity, and FIG. 32C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.018). FIGS. 33A, 33B and 33C are graphs showing aberrations of the zoom optical system ZL7 according to Example 7 in a telephoto end state (f=52.00), in which FIG. 33A is graphs showing various aberrations upon focusing on infinity, FIG. 33B is graphs showing coma aberration when an image blur is corrected (a vibration-proof lens group shift amount of 0.2 mm) upon focusing on infinity, and FIG. 33C is graphs showing various aberrations upon focusing on a short distant object (imaging magnification β=−0.027).

From each of the graphs showing aberration shown in FIGS. 31A-31C, 32A-32C and 33A-33C, the zoom optical system ZL7 according to Example 7 is found to have high imaging performance in which various aberrations are successfully corrected from the wide-angle end state to the telephoto end state. Moreover, the zoom optical system. ZL7 is found to have high imaging performance also upon correcting the image blur.

According to each Example described above, the zoom optical system having successful optical performance can be realized.

In addition, each Example described above shows one specific example of the zoom optical system according to each of the fifth and sixth embodiments, and the zoom optical systems according to the fifth and sixth embodiments are not limited thereto. In the fifth and sixth embodiments, the following content can be appropriately adopted within the range in which the optical performance is not adversely affected.

In Examples using numerical values according to the fifth and sixth embodiments, a three-group configuration was shown. However, the present invention can also be applied to other configurations such as a four-group configuration. For example, a configuration is allowed in which a lens or lens group is added thereto on a side closest to the object, or a configuration in which a lens or lens group is added thereto on a side closest to the image. Moreover, the lens group represents a part which is separated by the air distance which changes upon zooming or focusing and has at least one lens.

In the fifth and sixth embodiments, the zoom optical system may be formed into a focusing lens group in which focusing on an infinite distant object to a short distant object is made by moving a single lens group or a plurality of lens groups, or a partial lens group in the optical axis direction. The focusing lens group can also be applied to autofocusing, and is also suitable for a motor drive (using an ultrasonic motor, or the like) for autofocusing. In particular, at least a part of the third lens group G3 is preferably applied as the focusing lens group.

In the fifth and sixth embodiments, the zoom optical system may be formed into the vibration-proof lens group in which the image blur caused by camera shake is corrected by moving the lens group or the partial lens group so as to have the component in the direction perpendicular to the optical axis, or rotationally moving (swinging) the lens group or the partial lens group in an in-plane direction including the optical axis. In particular, at least a part of the third lens group G3 is preferably applied as the vibration-proof lens group.

In the fifth and sixth embodiments, a lens surface may be formed of a spherical surface or a flat surface, or formed of an aspherical surface. When the lens surface is spherical or flat, lens processing and assembly and adjustment are facilitated, and deterioration of optical performance by an error of the processing and assembly and adjustment can be prevented, and such a case is preferable. Moreover, when the lens surface is aspherical, the aspherical surface may be any aspherical surface, including an aspherical surface by grinding, a glass mold aspherical surface in which glass is formed into an aspherical surface shape by using a mold, and a composite type aspherical surface in which a resin is formed into the aspherical surface shape on a surface of glass. Moreover, the lens surface may be formed into a diffraction surface, or the lens may be formed into a gradient index lens (GRIN lens) or a plastic lens.

In the fifth and sixth embodiments, the aperture stop S is preferably arranged in a neighborhood of the third lens group G3 or within the third lens group G3. However, a lens frame may be used as substitution for such a role without providing a member as the aperture stop.

In the fifth and sixth embodiments, an antireflection film having high transmittance in a wide wavelength range may be applied to each lens surface in order to reduce a flare and a ghost to achieve high optical performance with high contrast.

The zoom optical systems ZL according to the fifth and sixth embodiments each have a zoom ratio of about 2 to 7.

EXPLANATION OF NUMERALS AND CHARACTERS

-   -   ZL (ZL1 to ZL7) Zoom optical system     -   G1 First lens group     -   G2 Second lens group     -   G3 Third lens group     -   S Aperture stop     -   I Image surface     -   1 Camera (imaging device)     -   2 Imaging lens (zoom optical system) 

The invention claimed is:
 1. A zoom optical system, comprising: in order from an object, a first lens group having positive refractive power; a second lens group having negative refractive power; and a third lens group having positive refractive power, wherein air distances between the first to third lens groups are varied upon zooming, the first lens group comprises a cemented lens disposed closest to the object, the cemented lens consisting of a negative lens and a positive lens in order from the object, the second lens group comprises at least two lenses having negative refractive power and at least one lens having positive refractive power, the third lens group has a positive single lens at its most object side, and the following conditional expressions are satisfied: 0.90<f3/fw≤1.03 2.00<ft/fw<7.00 4.40<f1/(−f2)<7.00 where f3 denotes a focal length of the third lens group, fw denotes a focal length of the zoom optical system in a wide-angle end state, ft denotes a focal length of the zoom optical system in a telephoto end state, f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group.
 2. The zoom optical system according to claim 1, wherein the positive single lens of the third lens group is moved for focusing.
 3. The zoom optical system according to claim 1, wherein focusing is effected by moving, as a focusing lens group, at least a part of the third lens group along an optical axis.
 4. The zoom optical system according to claim 3, wherein the focusing lens group is moved toward an image when a focusing state on a long-distance object is changed to a focusing state on a short-distance object.
 5. The zoom optical system according to claim 1, wherein, upon zooming from the wide-angle end state to a telephoto end state, an air distance between the first lens group and the second lens group is increased, and an air distance between the second lens group and the third lens group is decreased.
 6. The zoom optical system according to claim 1, further comprising: an aperture stop, and wherein the aperture stop is disposed between the second lens group and an image surface.
 7. The zoom optical system according to claim 6, wherein the aperture stop is disposed between the positive single lens of the third lens group and the image surface.
 8. The zoom optical system according to claim 1, wherein the first lens group is moved toward the object upon zooming from the wide-angle end state to a telephoto end state.
 9. The zoom optical system according to claim 1, including a vibration-proofing lens group on an image side of the second lens group for correcting image blur.
 10. The zoom optical system according to claim 9, wherein the vibration-proofing lens group is on an image side of the positive single lens of the third lens group.
 11. The zoom optical system according to claim 9, wherein the vibration-proofing lens group includes the positive single lens of the third lens group.
 12. An imaging device, comprising the zoom optical system according to claim
 1. 13. The zoom optical system according to claim 1, wherein the following conditional expression is satisfied: 5.20<f1/(−f2)<7.00.
 14. A method for manufacturing a zoom optical system, comprising: disposing, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, wherein the lens groups are arranged within a lens barrel in such a manner that: air distances between the first to third lens groups are varied upon zooming, the first lens group comprises a cemented lens disposed closest to the object, the cemented lens consisting of a negative lens and a positive lens in order from the object, the second lens group comprises at least two lenses having negative refractive power and at least one lens having positive refractive power, the third lens group has a positive single lens at its most object side, and the following conditional expressions are satisfied: 0.90<f3/fw≤1.03 2.00<ft/fw<7.00 4.40<f1/(−f2)<7.00 where f3 denotes a focal length of the third lens group, fw denotes a focal length of the zoom optical system in a wide-angle end state, ft denotes a focal length of the zoom optical system in a telephoto end state, f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group. 